研究者詳細 - 菱川　明栄

論文 - 菱川　明栄

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Wave-packet manipulation of He Rydberg states by a seeded free-electron laser 査読有り国際共著

Dumergue, M; Carpeggiani, PA; Csizmadia, T; Danailov, M; Demidovich, A; De Ninno, G; Di Fraia, M; Eng-Johnsson, P; Ertel, D; Fujise, H; Fushitani, M; Giannessi, L; Gopalakrishna, HN; Hishikawa, A; Ibrahim, H; Kühn, S; Légaré, F; Luo, Y; Maroju, PK; Mauritsson, J; Moioli, M; Olofsson, A; Peschel, J; Plekan, O; Pratt, ST; Raimondi, L; Ribic, PR; Saito, S; Sansone, G; Shah, R; Simpson, ER; You, D; Zangrando, M; Callegari, C; Ueda, K; Prince, KC

PHYSICAL REVIEW RESEARCH 6 巻 ( 4 ) 2024年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physical Review Research

We report a two-dimensional pump-control-probe spectroscopic study of the dynamics of singly excited He Rydberg-state wave packets with a seeded extreme ultraviolet (XUV) free-electron laser (FEL) source. A pair of coherent XUV pulses, defined by their coarse time separation and relative phase, created and manipulated the wave packets. The He atoms were postionized by infrared (IR) pulses, and the ion yield was measured as a function of XUV phase and IR arrival time. We tagged and sorted the relative phase of the XUV pulse pair on a single-shot basis by fitting each FEL spectrum with a suitable function that accounts for nonidealities of the XUV pulse pairs, associated with the seeding process; more generally, the fit returns the time-dependent electric field of the FEL spectra. The experimental two-dimensional maps of ion yields, measured as a function of IR (probe) delay and of XUV (pump-control) phase, were compared with the solution of the first-order time-dependent Schrödinger equation for this field. Despite the fact that the experimental conditions imply strong excitation, beyond the approximations of first-order perturbation theory, the simulated map satisfactorily reproduces the experimental one for temporally well-separated pulses. We show that by selecting data at appropriate values of pump-control phase, we enhance or suppress the amplitude of chosen wave-packet components consisting of two or more Rydberg states. When the temporal overlap of the pulse pair cannot be neglected, the phase reconstruction is underdetermined, and we provide a simplified comparison between data and simulations.

DOI： 10.1103/PhysRevResearch.6.043323

その他リンク： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevResearch.6.043323/fulltext

Ion-core switching in Rydberg series of XeKr 査読有り

Fukuda, Y; Szidarovszky, T; Nakata, M; Hishikawa, A; Yamanouchi, K

MOLECULAR PHYSICS 122 巻 ( 15-16 ) 2024年8月

State-selective dissociative double ionization of CH<sub>3</sub>I and CH<sub>2</sub>I<sub>2</sub> via I 4d core-hole states studied by multi-electron-ion coincidence spectroscopy 査読有り

Fushitani, M; Hikosaka, Y; Tashiro, M; Hishikawa, A

JOURNAL OF CHEMICAL PHYSICS 160 巻 ( 17 ) 2024年5月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Chemical Physics

The dissociative double ionization of CH3I and CH2I2 irradiated with extreme ultraviolet light at hv = 100 eV is investigated by multi-electron-ion coincidence spectroscopy using a magnetic bottle type electron spectrometer. The spin-orbit state-resolved Auger electron spectra for the I 4d core-hole states, (I 4d3/2)−1 and (I 4d5/2)−1, provide clear identifications of electronic states of CH3I2+ and CH2I22+. The dominant ion species produced after the double ionization correlate with the Auger electron energy, showing that different fragmentation pathways are open depending on the electronic states populated by the Auger decay. Theoretical calculations are performed to understand the fragmentation from the doubly charged states and the observed spin-orbit specificity in the Auger decay.

DOI： 10.1063/5.0204769

Exploring the ultrafast and isomer-dependent photodissociation of iodothiophenes <i>via</i> site-selective ionization 査読有り Open Access

Razmus, WO; Allum, F; Harries, J; Kumagai, Y; Nagaya, K; Bhattacharyya, S; Britton, M; Brouard, M; Bucksbaum, PH; Cheung, K; Crane, SW; Fushitani, M; Gabalski, I; Gejo, T; Ghrist, A; Heathcote, D; Hikosaka, Y; Hishikawa, A; Hockett, P; Jones, E; Kukk, E; Iwayama, H; Lam, HVS; McManus, JW; Milesevic, D; Mikosch, J; Minemoto, S; Niozu, A; Orr-Ewing, AJ; Owada, S; Rolles, D; Rudenko, A; Townsend, D; Ueda, K; Unwin, J; Vallance, C; Venkatachalam, A; Wada, S; Walmsley, T; Warne, EM; Woodhouse, JL; Burt, M; Ashfold, MNR; Minns, RS; Forbes, R

PHYSICAL CHEMISTRY CHEMICAL PHYSICS 26 巻 ( 16 ) 頁： 12725 - 12737 2024年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physical Chemistry Chemical Physics

C-I bond extension and fission following ultraviolet (UV, 262 nm) photoexcitation of 2- and 3-iodothiophene is studied using ultrafast time-resolved extreme ultraviolet (XUV) ionization in conjunction with velocity map ion imaging. The photoexcited molecules and eventual I atom products are probed by site-selective ionization at the I 4d edge using intense XUV pulses, which induce multiple charges initially localized to the iodine atom. At C-I separations below the critical distance for charge transfer (CT), charge can redistribute around the molecule leading to Coulomb explosion and charged fragments with high kinetic energy. At greater C-I separations, beyond the critical distance, CT is no longer possible and the measured kinetic energies of the charged iodine atoms report on the neutral dissociation process. The time and momentum resolved measurements allow determination of the timescales and the respective product momentum and kinetic energy distributions for both isomers, which are interpreted in terms of rival ‘direct’ and ‘indirect’ dissociation pathways. The measurements are compared with a classical over the barrier model, which reveals that the onset of the indirect dissociation process is delayed by ∼1 ps relative to the direct process. The kinetics of the two processes show no discernible difference between the two parent isomers, but the branching between the direct and indirect dissociation channels and the respective product momentum distributions show isomer dependencies. The greater relative yield of indirect dissociation products from 262 nm photolysis of 3-iodothiophene (cf. 2-iodothiophene) is attributed to the different partial cross-sections for (ring-centred) π∗ ← π and (C-I bond localized) σ∗ ← (n/π) excitation in the respective parent isomers.

DOI： 10.1039/d3cp06079a

Wave packet dynamics and control in excited states of molecular nitrogen 査読有り国際共著

Fushitani, M; Fujise, H; Hishikawa, A; You, D; Saito, S; Luo, Y; Ueda, K; Ibrahim, H; Légaré, F; Pratt, ST; Eng-Johnsson, P; Mauritsson, J; Olofsson, A; Peschel, J; Simpson, ER; Carpeggiani, PA; Ertel, D; Maroju, PK; Moioli, M; Sansone, G; Shah, RA; Csizmadia, T; Dumergue, M; Gopalakrishna, HN; Kühn, S; Callegari, C; Danailov, M; Demidovich, A; Raimondi, L; Zangrando, M; De Ninno, G; Di Fraia, M; Giannessi, L; Plekan, O; Ribic, PR; Prince, KC

JOURNAL OF CHEMICAL PHYSICS 160 巻 ( 10 ) 2024年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Chemical Physics

Wave packet interferometry with vacuum ultraviolet light has been used to probe a complex region of the electronic spectrum of molecular nitrogen, N2. Wave packets of Rydberg and valence states were excited by using double pulses of vacuum ultraviolet (VUV), free-electron-laser (FEL) light. These wave packets were composed of contributions from multiple electronic states with a moderate principal quantum number (n ∼ 4-9) and a range of vibrational and rotational quantum numbers. The phase relationship of the two FEL pulses varied in time, but as demonstrated previously, a shot-by-shot analysis allows the spectra to be sorted according to the phase between the two pulses. The wave packets were probed by angle-resolved photoionization using an infrared pulse with a variable delay after the pair of excitation pulses. The photoelectron branching fractions and angular distributions display oscillations that depend on both the time delays and the relative phases of the VUV pulses. The combination of frequency, time delay, and phase selection provides significant control over the ionization process and ultimately improves the ability to analyze and assign complex molecular spectra.

DOI： 10.1063/5.0188182

Imaging Ultrafast Dissociation Dynamics: OCS & Roaming in Formaldehyde 国際共著 Open Access

Endo, T; Neville, SP; Ziems, KM; Lassonde, P; Qu, C; Schmidt, BE; Fujise, H; Fushitani, M; Hishikawa, A; Grafe, S; Houston, PL; Bowman, JM; Schuurman, MS; Legare, F; Ibrahim, H

PROCEEDINGS OF THE 8TH INTERNATIONAL CONFERENCE ON ATTOSECOND SCIENCE AND TECHNOLOGY, ATTO 2023 300 巻頁： 75 - 82 2024年

出版者・発行元：Springer Proceedings in Physics

Upon photoexcitation, molecules break apart, following different dissociation reactions. We can image these dissociation pathways using Coulomb explosion imaging (CEI) and sometimes we can control them using asymmetric laser fields. In the formaldehyde molecule, we can see fragments following the direct, conventional dissociation path, as well as fragments deviating from this minimum energy path. So-called roaming fragments or “roamers” explore the potential energy landscape in a statistical manner and could be directly captured in real-time, despite the signal’s statistical character. This is possible due to the single-molecule sensitivity of CEI and we could show that the onset of roaming occurs actually several orders of magnitude earlier than previously expected. In the polar molecule OCS we go one step further by controlling the fragmentation process using two-color asymmetric laser fields. In addition to expected direct ionization effects, we also see post-ionization contributions, which are usually not visible in heavy polar molecules. We thus show in two different examples that CEI provides the means to extract new, unexpected pathways, which would otherwise remain hidden underneath a strong background.

DOI： 10.1007/978-3-031-47938-0_8

Dissociative ionization and Coulomb explosion of CH<sub>4</sub> in two-color asymmetric intense laser fields 査読有り国際共著

Hasegawa, H; Matsuda, A; Morishita, T; Madsen, LB; Jensen, F; Tolstikhin, OI; Hishikawa, A

PHYSICAL CHEMISTRY CHEMICAL PHYSICS 25 巻 ( 37 ) 頁： 25408 - 25419 2023年9月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physical Chemistry Chemical Physics

Directional fragment ejection from a tetrahedral molecule CH4 in linearly polarized two-color (ω and 2ω) asymmetric intense laser fields (50 fs, 1.4 × 1014 W cm−2, 800 nm and 400 nm) has been studied by three-dimensional ion coincidence momentum imaging. The H+ fragment produced from dissociative ionization, CH4 → H+ + CH3 + e−, is preferentially ejected on the larger amplitude side of the laser electric fields. Comparison with theoretical predictions by weak-field asymptotic theory shows that the observed asymmetry can be understood by the orientation selective tunneling ionization from the triply degenerated highest occupied molecular orbital (1t2) of CH4. A similar directional ejection of H+ was also observed for the low kinetic energy components of the two-body Coulomb explosion, CH4 → H+ + CH3+ + 2e−. On the other hand, the fragment ejection in the opposite direction were observed for the high energy component, as well as H2+ produced from the Coulomb explosion CH4 → H2+ + CH2+ + 2e−. Possible origins of the characteristic fragmentation are discussed.

DOI： 10.1039/d3cp02337k

Capturing transient core-to-core resonances in Kr in intense extreme-ultraviolet laser fields by electron-ion coincidence spectroscopy 査読有り

Fushitani, M; Yamada, M; Fujise, H; Owada, S; Togashi, T; Nakajima, K; Yabashi, M; Matsuda, A; Hikosaka, Y; Hishikawa, A

PHYSICAL REVIEW A 107 巻 ( 2 ) 頁： L021101 2023年2月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physical Review A

Resonances between core-hole states have been long hypothesized to understand nonlinear responses of atoms and molecules exposed to intense x-ray free-electron laser (XFEL) pulses, but evaded clear identification in previous studies due to their transient nature. Here we report clear evidence of core-to-core resonances by state-of-the-art electron-ion coincidence spectroscopy on Kr atoms. The observed 3p-3d resonance manifested the significance in multiple ionization to highly charged states against the ultrafast core-hole decay. The present study, elucidating the role of the core-to-core resonance in electronic responses of matter to high-frequency laser fields, will advance our understanding of nonlinear spectroscopy and ultrafast imaging by ultrashort intense EUV and x-ray pulses.

DOI： 10.1103/PhysRevA.107.L021101

その他リンク： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevA.107.L021101/fulltext

Orbital effects on tunnel-electron momentum distributions: Ar and H2 studied by electron-ion coincidence momentum imaging 査読有り Open Access

Ikeya, D; Fujise, H; Inaba, S; Takahashi, M; Yamamoto, M; Nakamura, T; Nagao, Y; Matsuda, A; Fushitani, M; Hishikawa, A

JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA 262 巻頁： 147280 - 147280 2023年1月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Electron Spectroscopy and Related Phenomena

Three-dimensional momentum distributions of tunnel-electrons produced from Ar and H2 in circularly polarized intense laser fields (1035 nm, 35 fs, 2×1014 W/cm2) have been measured by electron–ion coincidence momentum imaging. The photoelectrons recorded with a gas mixture of Ar and H2 exhibit torus-like distributions in the momentum space. Although ionization potentials are similar (15.8 eV for Ar and 15.4 eV for H2), significant differences are identified in the radius and the width of the photoelectron torus recorded in coincidence with the counterpart ions (Ar+ and H2+). The differences are confirmed by theoretical calculations based on the strong-field approximation, showing that the orbital character of ionizing electrons is encoded in the momentum distribution of tunnel electrons.

DOI： 10.1016/j.elspec.2022.147280

Imaging and Controlling ultrafast Dissociation Dynamics; from conventional to surprising paths

Endo T., Neville S.P., Lassonde P., Qu C., Schmidt B.E., Fushitani M., Hishikawa A., Houston P.L., Bowman J.M., Schuurman M.S., Légaré F., Ibrahim H.

Proceedings of SPIE - The International Society for Optical Engineering 12419 巻 2023年

出版者・発行元：Proceedings of SPIE - The International Society for Optical Engineering

Upon photo-excitation of a molecule it will break apart. We can see fragments following direct, conventional dissociation paths, as well as fragments deviating from this minimum energy path. The latter are called roaming fragments and explore the potential energy landscape in a statistical manner. Dissociating and roaming fragments are directly captured using Coulomb explosion imaging (CEI) and individual pathways are distinguished based on state-of-the-art theory analysis.

DOI： 10.1117/12.2649247

Following ultrafast Roaming Dissociation Dynamics with Coulomb Explosion Imaging

Endo T., Neville S., Lassonde P., Qu C., Fujise H., Fushitani M., Hishikawa A., Houston P., Bowman J., Légaré F., Schuurman M., Ibrahim H.

2023 Conference on Lasers and Electro-Optics, CLEO 2023 2023年

Following ultrafast Roaming Dissociation Dynamics with Coulomb Explosion Imaging

Endo T., Neville S., Lassonde P., Qu C., Fujise H., Fushitani M., Hishikawa A., Houston P., Bowman J., Légaré F., Schuurman M., Ibrahim H.

CLEO: Fundamental Science, CLEO:FS 2023 2023年

Asymmetric Dissociative Tunneling Ionization of Tetrafluoromethane in ω-2ω Intense Laser Fields 招待有り査読有り Open Access

Hasegawa, H; Walmsley, T; Matsuda, A; Morishita, T; Madsen, LB; Jensen, F; Tolstikhin, OI; Hishikawa, A

FRONTIERS IN CHEMISTRY 10 巻 2022年4月

担当区分：最終著者,　責任著者掲載種別：研究論文（学術雑誌）出版者・発行元：Frontiers in Chemistry

Dissociative ionization of tetrafluoromethane (CF4) in linearly polarized ω-2ω ultrashort intense laser fields (1.4 × 1014 W/cm2, 800 and 400 nm) has been investigated by three-dimensional momentum ion imaging. The spatial distribution of (Formula presented.) produced by CF4 → (Formula presented.) + F + e− exhibited a clear asymmetry with respect to the laser polarization direction. The degree of the asymmetry varies by the relative phase of the ω and 2ω laser fields, showing that 1) the breaking of the four equivalent C-F bonds can be manipulated by the laser pulse shape and 2) the C-F bond directed along the larger amplitude side of the ω-2ω electric fields tends to be broken. Weak-field asymptotic theory (WFAT) shows that the tunneling ionization from the 4t2 second highest-occupied molecular orbital (HOMO-1) surpasses that from the 1t1 HOMO. This predicts the enhancement of the tunneling ionization with electric fields pointing from F to C, in the direction opposite to that observed for the asymmetric fragment ejection. Possible mechanisms involved in the asymmetric dissociative ionization, such as post-ionization interactions, are discussed.

DOI： 10.3389/fchem.2022.857863

Helicity-dependent dissociative tunneling ionization of CF<sub>4</sub> in multicycle circularly polarized intense laser fields 査読有り

Fujise, H; Uemura, M; Hasegawa, H; Ikeya, D; Matsuda, A; Morishita, T; Madsen, LB; Jensen, F; Tolstikhin, OI; Hishikawa, A

PHYSICAL CHEMISTRY CHEMICAL PHYSICS 24 巻 ( 15 ) 頁： 8962 - 8969 2022年4月

担当区分：最終著者,　責任著者掲載種別：研究論文（学術雑誌）出版者・発行元：Physical Chemistry Chemical Physics

Dissociative tunneling ionization of tetrafluoromethane (CF4) in circularly polarized ultrashort intense laser fields (35 fs, 0.8 × 1014 W cm−2, 1035 nm), CF4 → CF4+ + e− → CF3+ + F + e−, has been studied by three-dimensional electron-ion coincidence momentum imaging. The photoelectron angular distribution in the recoil frame revealed that the dissociative tunneling ionization occurs efficiently when the laser electric field points from F to C. The obtained results are qualitatively consistent with the theoretical predictions by the weak-field asymptotic theory (WFAT) for tunneling ionization from the highest and next-highest occupied molecular orbitals, HOMO (1t1), and HOMO−1 (4t2), respectively. On the other hand, the angular distribution shows clear dependences on the polarization helicity, indicating that the breaking of the C-F bonds is sensitive to the helicity of the multicycle circularly polarized laser fields.

DOI： 10.1039/d1cp05858d

Post-Ionization Dynamics of the Polar Molecule OCS in Asymmetric Laser Fields 招待有り査読有り国際共著 Open Access

Endo, T; Ziems, KM; Richter, M; Fröbel, FG; Hishikawa, A; Gräfe, S; Légaré, F; Ibrahim, H

FRONTIERS IN CHEMISTRY 10 巻 2022年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Frontiers in Chemistry

We have investigated the dissociation mechanisms of the prototypical heavy polar molecule OCS into the two break-up channels of the dication, OCS2+ → O+ + CS+ and OC+ + S+, in phase-locked two-color intense laser fields. The branching ratio of the breaking of the C–O and C–S bonds followed a pronounced 2π-oscillation with a modulation depth of 11%, depending on the relative phase of the two-color laser fields. The fragment ejection direction of both break-up channels reflects the anisotropy of the tunneling ionization rate, following a 2π-periodicity, as well. The two dissociation pathways in the C–S bond breaking channel show different phase dependencies of the fragment ejection direction, which are assigned to post-ionization dynamics. These observations, resulting from the excitation with asymmetric two-color intense laser fields, supported by state-of-the-art theoretical simulations, reveal the importance of post-ionization population dynamics in addition to tunneling ionization in the molecular fragmentation processes, even for heavy polar molecules.

DOI： 10.3389/fchem.2022.859750

Electronic relaxation and dissociation dynamics in formaldehyde: pump wavelength dependence 査読有り Open Access

Endo, T; Neville, SP; Lassonde, P; Qu, C; Fujise, H; Fushitani, M; Hishikawa, A; Houston, PL; Bowman, JM; Légaré, F; Schuurman, MS; Ibrahim, H

PHYSICAL CHEMISTRY CHEMICAL PHYSICS 24 巻 ( 3 ) 頁： 1779 - 1786 2022年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physical Chemistry Chemical Physics

The effect of the incident UV pump wavelength on the subsequent excited state dynamics, electronic relaxation, and ultimate dissociation of formaldehyde is studied using first principles simulation and Coulomb explosion imaging (CEI) experiments. Transitions in a vibronic progression in the Ã ← X absorption band are systematically prepared using a tunable UV source which generates pulses centered at 304, 314, 329, and 337 nm. We find, both via ab initio simulation and experimental results, that the rate of excited state decay and subsequent dissociation displays a prominent dependence on which vibronic transition in the absorption band is prepared by the pump. Our simulations predict that nonadiabatic transition rates and dissociation yields will increase by a factor of >100 as the pump wavelength is decreased from 337 to 304 nm. The experimental results and theoretical simulations are in broad agreement and both indicate that the dissociation rate plateaus rapidly after ≈2 ps following an ultrafast sub-ps rise. This journal is

DOI： 10.1039/d1cp04264e

Electron-ion Coincidence Imaging of O<inf>2</inf> in Intense Laser Fields with Additional Dissociation Pulses

Ikeya D., Matsuda A., Fushitani M., Hishikawa A.

Optics InfoBase Conference Papers 2022年

Selective-bond breaking of CF<inf>4</inf> in phase-locked ω-2ω intense laser fields

Hasegawa H., Walmsley T., Matsuda A., Morishita T., Madsen L.B., Jensen F., Tolstikhin O.I., Hishikawa A.

Optics InfoBase Conference Papers 2022年

Roaming in Formaldehyde – and how to get there

Endo T., Neville S.P., Lassonde P., Qu C., Fujise H., Fushitani M., Hishikawa A., Houston P.L., Bowman J.M., Légaré F., Schuurman M.S., Ibrahim H.

Optics InfoBase Conference Papers 2022年

Post-Ionization Interaction of OCS in Phase-Locked Two-Color Laser Fields

Endo T., Ziems K.M., Richter M., Froebel F.G., Hishikawa A., Gräfe S., Légaré F., Ibrahim H.

Optics InfoBase Conference Papers 2022年

Selective-bond breaking of CF4 in phase-locked ω-2ω intense laser fields

Hiroka Hasegawa, Tiffany Walmsley, Akitaka Matsuda, Toru Morishita, Lars Bojer Madsen, Frank Jensen, Oleg I. Tolstikhin, Akiyoshi Hishikawa

The International Conference on Ultrafast Phenomena (UP) 2022 2022年

Association Reaction of Gaseous C<sub>2</sub>H<sub>4</sub> in Femtosecond Laser Filaments Studied by Time-of-Flight Mass Spectrometry 査読有り Open Access

Matsuda, A; Tani, K; Takeuchi, Y; Hayakawa, Y; Hishikawa, A

ACS OMEGA 6 巻 ( 44 ) 頁： 29862 - 29868 2021年11月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACS Omega

Association reactions by femtosecond laser filamentation in gaseous C2H4 were studied by time-of-flight mass spectrometry of neutral reaction products. Direct sampling from the reaction cell to a mass spectrometer via a differential pumping stage allowed the identification of various hydrocarbon molecules CnHm with n = 3-7 and m = 4-7, which includes species not observed in the previous studies. It was found that products containing three and four carbon atoms dominate the mass spectrum with smaller yields for higher-mass species, suggesting that carbon chain growth proceeds through the reaction with C2H4 in the reaction cell. The product distribution showed a clear dependence on the laser pulse energy for filamentation.

DOI： 10.1021/acsomega.1c04354

Time-resolved shot-by-shot photoelectron spectroscopy of autoionizing Xe<SUP>+</SUP> states by EUV-free-electron-laser and near-IR laser pulses 査読有り

Fushitani, M; Kawabe, Y; Fujise, H; Yamada, M; Hasegawa, H; Owada, S; Togashi, T; Nakajima, K; Yabashi, M; Matsuda, A; Hikosaka, Y; Hishikawa, A

PHYSICAL REVIEW A 104 巻 ( 2 ) 2021年8月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physical Review A

Ultrafast dynamics of highly excited Rydberg states of is investigated by time-resolved shot-by-shot photoelectron spectroscopy with EUV-free-electron-laser pump (40.8 eV) and near-infrared probe (1.56 eV) pulses. Sorting the single-shot spectra in the order of relative delay between the two pulses allows for investigating ultrafast decays of intermediate states participating in the double ionization of Xe. Observed photoelectron spectra show a biexponential decay within ∼100 fs and ∼300 ps in addition to constant signals lasting longer than 1 ns. These ultrafast decays reflect the lifetimes of autoionizing Rydberg states converging to electronically excited states of . The results demonstrate that time-resolved shot-by-shot EUV-free-electron-laser photoelectron spectroscopywith a synchronized optical laser provides a powerful tool for investigating ultrafast electron emission processes.

DOI： 10.1103/PhysRevA.104.023102

その他リンク： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevA.104.023102/fulltext

Time-resolved photoelectron imaging of complex resonances in molecular nitrogen 査読有り国際共著 Open Access

Fushitani, M; Pratt, ST; You, D; Saito, S; Luo, Y; Ueda, K; Fujise, H; Hishikawa, A; Ibrahim, H; Légaré, F; Johnsson, P; Peschel, J; Simpson, ER; Olofsson, A; Mauritsson, J; Carpeggiani, PA; Maroju, PK; Moioli, M; Ertel, D; Shah, R; Sansone, G; Csizmadia, T; Dumergue, M; Harshitha, NG; Kühn, S; Callegari, C; Plekan, O; Di Fraia, M; Danailov, MB; Demidovich, A; Giannessi, L; Raimondi, L; Zangrando, M; De Ninno, G; Prince, KC

JOURNAL OF CHEMICAL PHYSICS 154 巻 ( 14 ) 頁： 144305 - 144305 2021年4月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Chemical Physics

We have used the FERMI free-electron laser to perform time-resolved photoelectron imaging experiments on a complex group of resonances near 15.38 eV in the absorption spectrum of molecular nitrogen, N2, under jet-cooled conditions. The new data complement and extend the earlier work of Fushitani et al. [Opt. Express 27, 19702-19711 (2019)], who recorded time-resolved photoelectron spectra for this same group of resonances. Time-dependent oscillations are observed in both the photoelectron yields and the photoelectron angular distributions, providing insight into the interactions among the resonant intermediate states. In addition, for most states, we observe an exponential decay of the photoelectron yield that depends on the ionic final state. This observation can be rationalized by the different lifetimes for the intermediate states contributing to a particular ionization channel. Although there are nine resonances within the group, we show that by detecting individual photoelectron final states and their angular dependence, we can identify and differentiate quantum pathways within this complex system.

DOI： 10.1063/5.0046577

その他リンク： https://aip.scitation.org/doi/pdf/10.1063/5.0046577

On the measurement of statistical dynamics using the method of Coulomb explosion imaging

Endo T., Neville S.P., Wanie V., Beaulieu S., Qu C., Lassonde P., Schmidt B.E., Fujise H., Fushitani M., Hishikawa A., Houston P.L., Bowman J.M., Schuurman M.S., Légaré F., Ibrahim H.

AIP Conference Proceedings 2343 巻 2021年3月

記述言語：日本語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：AIP Conference Proceedings

Using time-resolved Coulomb explosion imaging (CEI) in an ultraviolet (UV) pump near infrared (NIR) probe experiment, we directly image the different dissociation dynamics in the formaldehyde molecule. Different pathways are distinguished from each other, despite their statistical nature. To extract such dynamics, hidden in a statistical background, calls for an elimination of noise. In our approach, we take advantage of CEI being a quasi-background-free technique.

DOI： 10.1063/5.0047930

Capturing roaming molecular fragments in real time 査読有り国際共著国際誌

Endo, T; Neville, SP; Wanie, V; Beaulieu, S; Qu, C; Deschamps, J; Lassonde, P; Schmidt, BE; Fujise, H; Fushitani, M; Hishikawa, A; Houston, PL; Bowman, JM; Schuurman, MS; Légaré, F; Ibrahim, H

SCIENCE 370 巻 ( 6520 ) 頁： 1072 - + 2020年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Science

Since the discovery of roaming as an alternative molecular dissociation pathway in formaldehyde (H2CO), it has been indirectly observed in numerous molecules. The phenomenon describes a frustrated dissociation with fragments roaming at relatively large interatomic distances rather than following conventional transition-state dissociation; incipient radicals from the parent molecule self-react to form molecular products. Roaming has been identified spectroscopically through static product channel- resolved measurements, but not in real-time observations of the roaming fragment itself. Using timeresolved Coulomb explosion imaging (CEI), we directly imaged individual "roamers"on ultrafast time scales in the prototypical formaldehyde dissociation reaction. Using high-level first-principles simulations of all critical experimental steps, distinctive roaming signatures were identified. These were rendered observable by extracting rare stochastic events out of an overwhelming background using the highly sensitive CEI method.

DOI： 10.1126/science.abc2960

Capturing roaming fragments in real time: A molecular road movie

Endo T., Neville S.P., Wanie V., Beaulieu S., Qu C., Deschamps J., Lassonde P., Schmidt B.E., Fujise H., Fushitani M., Hishikawa A., Houston P.L., Bowman J.M., Schuurman M.S., Légaré F., Ibrahim H.

Optics InfoBase Conference Papers 2020年11月

記述言語：日本語出版者・発行元：Optics InfoBase Conference Papers

"Roamers" are directly observed in the prototypical roaming reaction in the formaldehyde molecule. Despite their statistical nature, roaming is well discriminated from the radical- and molecular dissociation channels, using Coulomb explosion imaging and theoretical modeling.

DOI： 10.1364/UP.2020.Th4A.1

Ultrafast Reaction Imaging and Control by Ultrashort Intense Laser Pulses 招待有り査読有り Open Access

Hishikawa, A; Matsuda, A; Fushitani, M

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 93 巻 ( 11 ) 頁： 1293 - 1304 2020年11月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Bulletin of the Chemical Society of Japan

Molecules irradiated with intense laser pulses (field intensity ∼1015W/cm2) exhibit a variety of characteristic processes, such as tunneling ionization, electron rescattering, high-order harmonics generation and Coulomb explosion, that cannot be seen in a weak light field. These features have attracted attention in the last decades as they provide unique approaches to visualize and manipulate ultrafast dynamics of atoms and molecules. Here we discuss molecular processes in intense laser fields, with focuses on the applications to ultrafast imaging and control of reaction dynamics.

DOI： 10.1246/bcsj.20200158

Characterization of soft X-ray FEL pulse duration with two-color photoelectron spectroscopy 査読有り

Owada, S; Fushitani, M; Matsuda, A; Fujise, H; Sasaki, Y; Hikosaka, Y; Hishikawa, A; Yabashi, M

JOURNAL OF SYNCHROTRON RADIATION 27 巻 ( 5 ) 頁： 1362 - 1365 2020年9月

Multielectron-Ion Coincidence Spectroscopy of Xe in Extreme Ultraviolet Laser Fields: Nonlinear Multiple Ionization via Double Core-Hole States 査読有り国際誌

Fushitani, M; Sasaki, Y; Matsuda, A; Fujise, H; Kawabe, Y; Hashigaya, K; Owada, S; Togashi, T; Nakajima, K; Yabashi, M; Hikosaka, Y; Hishikawa, A

PHYSICAL REVIEW LETTERS 124 巻 ( 19 ) 2020年5月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physical Review Letters

Ultrafast multiphoton ionization of Xe in strong extreme ultraviolet free-electron laser (FEL) fields (91 eV, 30 fs, 1.6×1012 W/cm2) has been investigated by multielectron-ion coincidence spectroscopy. The electron spectra recorded in coincidence with Xe4+ show characteristic features associated with two-photon absorption to the 4d-2 double core-hole (DCH) states and subsequent Auger decay. It is found that the pathway via the DCH states, which has eluded clear identification in previous studies, makes a large contribution to the multiple ionization, despite the long FEL pulse duration compared with the lifetime of the 4d core-hole states.

DOI： 10.1103/PhysRevLett.124.193201

その他リンク： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevLett.124.193201/fulltext

Angle dependence of dissociative tunneling ionization of NO in asymmetric two-color intense laser fields 査読有り

Endo, T; Fujise, H; Hasegawa, H; Matsuda, A; Fushitani, M; Tolstikhin, OI; Morishita, T; Hishikawa, A

PHYSICAL REVIEW A 100 巻 ( 5 ) 頁： 053422 2019年11月

担当区分：最終著者,　責任著者記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Physical Review A

Dissociative tunneling ionization of nitric oxide (NO) in linearly polarized phase-locked two-color femtosecond intense laser fields (45 fs, λ=800 and 400 nm, total field intensity I=1×1014W/cm2) has been studied by three-dimensional ion momentum imaging. The N+ fragment produced by the dissociative ionization, NO→NO++e-→N++O+e-, exhibits a butterflylike momentum distribution peaked at finite angles with respect to the laser polarization direction. In addition, a clear dependence on the relative phase between the two laser fields is observed, showing that the tunneling ionization occurs efficiently when the electric field points from N to O. For the highest kinetic energy component, the observed orientation dependence is well explained with theoretical calculations by the weak-field asymptotic theory for the 2πhighest occupied molecular orbital (HOMO). On the other hand, the peak angle shifts toward the laser polarization direction as the kinetic energy decreases, indicating that pathways other than direct ionization from the HOMO contribute to the dissociative ionization.

DOI： 10.1103/PhysRevA.100.053422

Probing Rydberg-Rydberg interactions in N<sub>2</sub> by ultrafast EUV-NIR photoelectron spectroscopy 査読有り国際共著 Open Access

Fushitani, M; Toida, Y; Légaré, F; Hishikawa, A

OPTICS EXPRESS 27 巻 ( 14 ) 頁： 19702 - 19711 2019年7月

担当区分：最終著者,　責任著者記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Optics Letters

The ultrafast dynamics of molecular nitrogen (N2) just below the ionization threshold has been investigated by time-resolved photoelectron spectroscopy using a single harmonic centered at hν = 15.38 eV. The evolution of the Rydberg wavepacket launched by the ultrashort EUV pulse is probed by a time-delayed femtosecond NIR laser pulse. The observed photoelectron spectra show two series of vibrational peaks to the ground X2Σg+ state and the first excited A2Πu state of N+2 . Among these, two photoelectron peaks with the vibrational quantum numbers vX+ = 4 and vA+ = 1 exhibit clear anti-phase oscillations with a period of 300 fs, showing that two Rydberg states converging to the X2Σg+ and A2Πu ionic states interact with each other, thus causing periodic switching in the population of the ion core states.

DOI： 10.1364/OE.27.019702

Coincidence momentum imaging of four- and three-body Coulomb explosion of formaldehyde in ultrashort intense laser fields 査読有り国際共著

Tseng, CM; Fushitani, M; Matsuda, A; Hishikawa, A

JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA 228 巻頁： 25 - 30 2018年10月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Electron Spectroscopy and Related Phenomena

Ion-coincidence momentum imaging of Coulomb explosion of formaldehyde (H2CO) in femtosecond intense laser fields (800 nm, 1.3 × 1015 W/cm2) is performed with two different laser pulse durations (7 fs and 35 fs). In the 7-fs laser fields, the full fragmentation pathway from H2CO4+ → H+ + H+ + C+ + O+ is identified. The angles between the fragment momenta are well reproduced by a simple Coulomb explosion model from the geometry of neutral formaldehyde, showing that the molecular structure is virtually frozen along the bending coordinates during the multiple ionization. Three-body Coulomb explosion pathways from triply charged states, H2CO3+ → H+ + H+ + CO+ and H+ + CH+ + O+, are observed in both the 7-fs and 35-fs laser fields. Significant changes in the momentum angle distribution and asymmetric energy partitioning between two H+ ions are observed in the 35-fs case, which are attributed to structural deformation prior to the Coulomb explosion in the longer pulse.

DOI： 10.1016/j.elspec.2018.07.001

Femtosecond laser filamentation in gaseous ethylene: Formation of hydrogenated amorphous carbon 査読有り

A. Matsuda, T. Hayashi, R. Kitaura, A. Hishikawa

Chem. Lett. 46 巻頁： 1426-1429 2017年7月

Selective bond breaking of CO<sub>2</sub> in phase-locked two-color intense laser fields: laser field intensity dependence 査読有り Open Access

Endo, T; Fujise, H; Kawachi, Y; Ishihara, A; Matsuda, A; Fushitani, M; Kono, H; Hishikawa, A

PHYSICAL CHEMISTRY CHEMICAL PHYSICS 19 巻 ( 5 ) 頁： 3550 - 3556 2017年2月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physical Chemistry Chemical Physics

Selective bond breaking of CO2 in phase-locked ω-2ω two-color intense laser fields (λ = 800 nm and 400 nm, total field intensity I ∼ 1014 W cm-2) has been investigated by coincidence momentum imaging. The CO+ and O+ fragment ions produced by two-body Coulomb explosion, CO22+ → CO+ + O+, exhibit asymmetric distributions along the laser polarization direction, showing that one of the two equivalent C-O bonds is selectively broken by the laser fields. At a field intensity higher than 2 × 1014 W cm-2, the largest fragment asymmetry is observed when the relative phase between the ω and 2ω laser fields is ∼0 and π. On the other hand, an increase of the asymmetry and a shift of the phase providing the largest asymmetry are observed at lower field intensities. The selective bond breaking and its dependence on the laser field intensity are discussed in terms of a mechanism involving deformation of the potential energy surfaces and electron recollision in intense laser fields.

DOI： 10.1039/c6cp07471e

Single-order laser high harmonics in XUV for ultrafast photoelectron spectroscopy of molecular wavepacket dynamics 査読有り Open Access

Fushitani, M; Hishikawa, A

STRUCTURAL DYNAMICS-US 3 巻 ( 6 ) 頁： 062602 2016年11月

担当区分：最終著者,　責任著者記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Structural Dynamics

We present applications of extreme ultraviolet (XUV) single-order laser harmonics to gas-phase ultrafast photoelectron spectroscopy. Ultrashort XUV pulses at 80 nm are obtained as the 5th order harmonics of the fundamental laser at 400 nm by using Xe or Kr as the nonlinear medium and separated from other harmonic orders by using an indium foil. The single-order laser harmonics is applied for real-time probing of vibrational wavepacket dynamics of I2 molecules in the bound and dissociating low-lying electronic states and electronic-vibrational wavepacket dynamics of highly excited Rydberg N2 molecules.

DOI： 10.1063/1.4964775

Imaging Electronic Excitation of NO by Ultrafast Laser Tunneling Ionization 査読有り

Endo, T; Matsuda, A; Fushitani, M; Yasuike, T; Tolstikhin, OI; Morishita, T; Hishikawa, A

PHYSICAL REVIEW LETTERS 116 巻 ( 16 ) 頁： 163002 2016年4月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physical Review Letters

Tunneling-ionization imaging of photoexcitation of NO has been demonstrated by using few-cycle near-infrared intense laser pulses (8 fs, 800 nm, 1.1×1014 W/cm2). The ion image of N+ fragment ions produced by dissociative ionization of NO in the ground state, NO (X2Π,2π)→NO++e-→N++O+e-, exhibits a characteristic momentum distribution peaked at 45° with respect to the laser polarization direction. On the other hand, a broad distribution centered at ∼0° appears when the A2Σ+ (3sσ) excited state is prepared as the initial state by deep-UV photoexcitation. The observed angular distributions are in good agreement with the corresponding theoretical tunneling ionization yields, showing that the fragment anisotropy reflects changes of the highest-occupied molecular orbital by photoexcitation.

DOI： 10.1103/PhysRevLett.116.163002

Photoelectron sidebands induced by a chirped laser field for shot-by-shot temporal characterization of FEL pulses 査読有り

Liu, CN; Morishita, T; Fushitani, M; Hishikawa, A

JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS 49 巻 ( 3 ) 頁： 034005 2016年2月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Physics B: Atomic, Molecular and Optical Physics

We theoretically investigate the laser-assisted photoionization of He by an extreme ultra violet (XUV) pulse in the presence of a linearly chirped intense laser pulse by solving the time-dependent Schrödinger equation within the single-active-electron approximation. Analysis based on the time-dependent perturbation theory is also carried out to provide more physical insights. A new scheme is shown to be capable of extracting the arrival time of an XUV free-electron laser (FEL) pulse relative to an external laser pulse as well as the XUV pulse duration from the photoelectron sidebands resulting from XUV ionization in the presence of a chirped laser pulse. This scheme is independent of the energy fluctuation and the timing jittering of the FEL pulse. Therefore it can be implemented in a non-invasive way to characterize FEL pulses on a shot-by-shot basis in time-resolved spectroscopy.

DOI： 10.1088/0953-4075/49/3/034005

Coincidence momentum imaging of asymmetric Coulomb explosion of CO<sub>2</sub> in phase-locked two-color intense laser fields 査読有り

Endo, T; Fujise, H; Matsuda, A; Fushitani, M; Kono, H; Hishikawa, A

JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA 207 巻頁： 50 - 54 2016年2月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Electron Spectroscopy and Related Phenomena

Coulomb explosion of CO2, CO2 → CO22+ + 2e- → CO+ + O+ + 2e-, in phase-locked two-color ultrashort intense laser fields (800 nm and 400 nm, ∼1014 W/cm2) has been investigated by coincidence momentum imaging. The momentum images of the O+ and CO+ fragments show asymmetric distributions along the laser polarization direction depending on the relative phase of the two-color laser fields. The fragment asymmetry becomes most prominent (∼4%) at the relative phases providing the largest asymmetry of the electric field amplitude, with the O+ fragments preferentially ejected to the stronger field side. The mechanism of the asymmetric bond breaking of the two equivalent C-O bonds is discussed in terms of the nuclear dynamics in CO22+.

DOI： 10.1016/j.elspec.2015.12.010

Femtosecond two-photon Rabi oscillations in excited He driven by ultrashort intense laser fields 査読有り

Fushitani, M; Liu, CN; Matsuda, A; Endo, T; Toida, Y; Nagasono, M; Togashi, T; Yabashi, M; Ishikawa, T; Hikosaka, Y; Morishita, T; Hishikawa, A

NATURE PHOTONICS 10 巻 ( 2 ) 頁： 102 - + 2016年2月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Nature Photonics

Coherent light-matter interaction provides powerful methods for manipulating quantum systems. Rabi oscillation is one such process. As it enables complete population transfer to a target state, it is thus routinely exploited in a variety of applications in photonics, notably quantum information processing. The extension of coherent control techniques to the multiphoton regime offers wider applicability, and access to highly excited or dipole-forbidden transition states. However, the multiphoton Rabi process is often disrupted by other competing nonlinear effects such as the a.c. Stark shift, especially at the high laser-field intensities necessary to achieve ultrafast Rabi oscillations. Here we demonstrate a new route to drive two-photon Rabi oscillations on timescales as short as tens of femtoseconds, by utilizing the strong-field phenomenon known as Freeman resonance. The scenario is not specific to atomic helium as investigated in the present study, but broadly applicable to other systems, thus opening new prospects for the ultrafast manipulation of Rydberg states.

DOI： 10.1038/NPHOTON.2015.228

Correlation between Photoeletron and Photoion in Ultrafast Multichannel Photoionization of Ar 査読有り

Itakura, R; Fushitani, M; Hishikawa, A; Sako, T

INTERNATIONAL CONFERENCE OF COMPUTATIONAL METHODS IN SCIENCES AND ENGINEERING 2015 (ICCMSE 2015) 1702 巻 2015年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：AIP Conference Proceedings

We theoretically investigate coherent dynamics of ions created through ultrafast multichannel photoionization from a viewpoint of photoelectron-photoion correlation. The model calculation on single-photon ionization of Ar reveals that the coherent hole dynamics in Ar+ associated with a superposition of the spin-orbit states 2PJ (J = 3/2 and 1/2) can be identified by monitoring only the photoion created by a Fourier-transform limited extreme ultraviolet (EUV) pulse with the fs pulse duration, while the coherence is lost by a chirped EUV pulse. It is demonstrated that by coincidence detection of the photoelectron and photoion the coherent hole dynamics can be extracted even in the case of ionization by a chirped EUV pulse with the sufficiently wide bandwidth.

DOI： 10.1063/1.4938829

Ion-Coincidence Momentum Imaging of Three-Body Coulomb Explosion of Formaldehyde in Ultrashort Intense Laser Fields 査読有り

Fushitani, M; Tseng, CM; Matsuda, A; Hishikawa, A

INTERNATIONAL CONFERENCE OF COMPUTATIONAL METHODS IN SCIENCES AND ENGINEERING 2015 (ICCMSE 2015) 1702 巻 2015年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：AIP Conference Proceedings

Three-body Coulomb explosion of formaldehyde (H2CO) in intense 7- and 35-fs laser fields (1.3 × 1015 W/cm2) has been investigated by using ion-coincidence momentum imaging technique. Two types of explosion pathways from the triply charged state, H2CO3+ → (i) H+ + H+ + CO+ and (ii) H+ + CH+ + O+, have been identified. It is shown from the momentum correlation of the fragment ions of pathway (i), that the geometrical structure of the molecule is essentially frozen along the H-C-H bending coordinate for the 7-fs case. On the other hand, for a longer pulse duration (35 fs), structural deformation along the C-H stretching and H-C-H bending coordinates is identified, which is ascribed to the nuclear dynamics in the dication states populated within the laser pulse duration.

DOI： 10.1063/1.4938821

Fragment anisotropy on dissociative ionization of NO in two-color intense laser fields 査読有り

Endo Tomoyuki, Ishihara Ayaka, Matsuda Akitaka, Fushitani Mizuho, Hishikawa Akiyoshi

XXIX INTERNATIONAL CONFERENCE ON PHOTONIC, ELECTRONIC, AND ATOMIC COLLISIONS (ICPEAC2015), PTS 1-12 635 巻 ( 11 ) 2015年

記述言語：日本語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：Journal of Physics: Conference Series

Dissociative ionization of NO, NO → NO+ + e- → N+ + O + e-, in ω-2ω two-color phase-controlled intense laser fields was investigated by three-dimensional ion momentum imaging. The momentum image of the N+ ion exhibited anisotropic distributions peaked at 35° against the laser polarization, which show clear left-right asymmetry depending on the ω-2ω relative phase. The present study demonstrates that the molecular orbital can be retrieved by distinguishing the difference between the N and O side from the fragment anisotropy by intense laser pulses.

DOI： 10.1088/1742-6596/635/11/112027

Determination of Absolute Cross-Sections of Nonresonant EUV-UV Two-Color Two-Photon Ionization of He 査読有り

Fushitani, M; Hikosaka, Y; Matsuda, A; Endo, T; Shigemasa, E; Nagasono, M; Sato, T; Togashi, T; Yabashi, M; Ishikawa, T; Hishikawa, A

ULTRAFAST PHENOMENA XIX 162 巻頁： 109 - 112 2015年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：Springer Proceedings in Physics

Single-shot photoelectron spectroscopy was performed for nonresonant EUV-UV two-color two-photon ionization of He. From data analysis on the shotby- shot basis, the absolute cross-section was determined to be σ(2) (59.7 nm, 268 nm) = 4.1(6) × 10-52 cm4 s.

DOI： 10.1007/978-3-319-13242-6_26

Time-Resolved Coulomb Explosion Imaging of Ultrafast Fragmentation of CS<sub>2</sub> in Highly Charged States 査読有り

Matsuda, A; Takahashi, EJ; Hishikawa, A

ULTRAFAST PHENOMENA XIX 162 巻頁： 168 - 171 2015年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：Springer Proceedings in Physics

Time-resolved three-body Coulomb explosion imaging of dissociating CS2 in few-cycle intense laser fields (9 fs, 4 × 1015 W/cm2) is performed. It is revealed that the ultrafast fragmentation dynamics of CS2 in highly charged states proceed in a different timescale depending on the charge state.

DOI： 10.1007/978-3-319-13242-6_40

Ultrafast two-photon Rabi oscillations in excited He driven by femtosecond intense laser fields 査読有り

Hishikawa A., Fushitani M., Liu C. N., Matsuda A., Endo T., Toida Y., Hikosaka Y., Morishita T.

XXIX INTERNATIONAL CONFERENCE ON PHOTONIC, ELECTRONIC, AND ATOMIC COLLISIONS (ICPEAC2015), PTS 1-12 635 巻 ( 9 ) 2015年

記述言語：日本語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：Journal of Physics: Conference Series

We demonstrate ultrafast multiphoton coherent excitation in near-infrared intense laser fields (≤10 TW/cm2) using excited helium in the 1s2p (1P) state as the target. Strong two-photon coupling between the 2p state and the 5f and 6f Rydberg states drives ultrafast Rabi oscillations in tens of femtosecond. Theoretical calculations solving the time-dependent Schrodinger equation were carried out to elucidate the strong field effects.

DOI： 10.1088/1742-6596/635/9/092082

Five-photon sequential double ionization of He in intense extreme-ultraviolet free-electron laser fields 査読有り

Hikosaka, Y; Fushitani, M; Matsuda, A; Endo, T; Toida, Y; Shigemasa, E; Nagasono, M; Tono, K; Togashi, T; Yabashi, M; Ishikawa, T; Hishikawa, A

PHYSICAL REVIEW A 90 巻 ( 5 ) 頁： 053403 2014年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physical Review A - Atomic, Molecular, and Optical Physics

A multiphoton ionization process of He in intense extreme ultraviolet free-electron laser fields is investigated in a photon energy range of hv=20.1-20.8eV using shot-by-shot photoelectron spectroscopy. A photoelectron peak resulting from sequential double ionization of He due to five-photon absorption is observed around hv=20.4. Shot-by-shot analysis of photoelectron spectra shows that two-photon resonance to the He+(2s2S) state from the He+ ground state is responsible for the substantial enhancement of five-photon double ionization. Effective cross sections for two-photon absorption between the 1s and 2s states of He+ and for one-photon absorption from the He+ 2s state are obtained.

DOI： 10.1103/PhysRevA.90.053403

Photoelectron-photoion correlation in ultrafast multichannel photoionization of Ar 査読有り

Itakura, R; Fushitani, M; Hishikawa, A; Sako, T

JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS 47 巻 ( 19 ) 頁： 195602 2014年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Physics B: Atomic, Molecular and Optical Physics

Ultrafast multichannel single-photon ionization of Ar is investigated theoretically by a model calculation incorporating correlation between the photoelectron and photoion. It is shown that the coherent hole dynamics in Ar+associated with a superposition of the spin-orbit states can be observed by using a Fourier-transform limited laser pulse for ionization, while the coherence is degraded or lost by chirped a laser pulse. We demonstrate that the coherent hole dynamics can be retrieved even in the case of ionization by a chirped laser pulse, by labeling the photoion dynamics with the counterpart photoelectron energy.

DOI： 10.1088/0953-4075/47/19/195602

Time-resolved laser Coulomb explosion imaging using few-cycle intense laser pulses: Application to exploding CS<sub>2</sub> in highly charged states 査読有り

Matsuda, A; Takahashi, EJ; Hishikawa, A

JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA 195 巻頁： 327 - 331 2014年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Electron Spectroscopy and Related Phenomena

Ion-coincidence momentum imaging of three-body Coulomb explosion of CS2, CS2z+ → Sp+ + Cq+ + Sr+ (z = p + q + r), in few-cycle intense laser fields (9 fs, ∼1015 W/cm2) is presented. It is shown that the momentum distributions of fragment ions produced from CS210+ are well reproduced by a classical explosion model incorporating the coordinate and momentum distributions of the initial ground vibrational state of CS2. On the other hand, a significant deviation is observed for CS23+ due to the non-Coulombic character of the potential energy surfaces. Coulomb explosion imaging is applied to real-time probing of Coulomb exploding CS2 in highly charged states, using a pair of intense few-cycle laser pulses. It is shown that the explosion proceeds in a different time scale depending on the charge state, mostly along the linear geometry during the bond-breaking of the two CS bonds.

DOI： 10.1016/j.elspec.2013.12.011

Preface 査読有り

Daimon, H; Hishikawa, A; Miron, C

JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA 195 巻頁： 285 - 286 2014年8月

Special issue on ultrafast electron and molecular dynamics Preface 査読有り Open Access

Martin, F; Hishikawa, A; Vrakking, M

JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS 47 巻 ( 12 ) 2014年6月

Dissociative ionization of NO in few-cycle intense laser fields : Effects of π-σ electronic transition 査読有り

Endo Tomoyuki, Fushitani Mizuho, Matsuda Akitaka, Hishikawa Akiyoshi

XXVIII INTERNATIONAL CONFERENCE ON PHOTONIC, ELECTRONIC AND ATOMIC COLLISIONS (ICPEAC) 488 巻 ( SECTION 3 ) 2014年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：Journal of Physics: Conference Series

Dissociative ionization (DI) of NO in few-cycle intense laser fields was investigated by using the 3D momentum imaging method. It was found that the symmetry change in the outermost occupied molecular orbital upon the π-σ electronic transition is clearly reflected in the spatial anisotropy of the fragmention, N+.

DOI： 10.1088/1742-6596/488/3/032025

Resolving the enhanced nonlinear double excitation of helium in intense ultra-short extreme-ultraviolet pulses 査読有り

Liu Chien-Nan, Hishikawa Akiyoshi, Morishita Toru

XXVIII INTERNATIONAL CONFERENCE ON PHOTONIC, ELECTRONIC AND ATOMIC COLLISIONS (ICPEAC) 488 巻 ( SECTION 3 ) 2014年

記述言語：日本語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：Journal of Physics: Conference Series

We present a theoretical study for multiphoton double excitation of He atoms exposed to an intense ul-trashort extreme-ultraviolet (EUV) pulse, where the photon energy coincides with the transition energy from the ground state to a Rydberg state. We identify the mechanism of the enhanced three-photon absorption probability as observed in the experiment.

DOI： 10.1088/1742-6596/488/3/032047

Two-photon rabi oscillations of excited he atoms in ultrafast strong laser field ionization 査読有り

Fushitani M, Liu C.-N, Matsuda A, Endo T, Toida Y, Hikosaka Y, Nagasono M, Togashi T, Yabashi M, Ishikawa T, Morishita T, Hishikawa A

Optics InfoBase Conference Papers 2014年

Determination of absolute cross-sections of nonresonant EUV-UV two-color two-photon ionization of he

Fushitani M., Hikosaka Y., Matsuda A., Endo T., Shigemasa E., Nagasono M., Sato T., Togashi T., Yabashi M., Ishikawa T., Hishikawa A.

Optics InfoBase Conference Papers 2014年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：Optics InfoBase Conference Papers

Single-shot photoelectron spectroscopy was performed for nonresonant EUV-UV twocolor two-photon ionization of He. From data analysis on the shot-by-shot basis, the absolute cross-section was determined to be σ(2)(597nm, 268nm) = 4.1(6)×10-52 cm4 s. © 2014 OSA.

DOI： 10.1364/up.2014.08.tue.p2.5

Ultrafast photoelectron spectroscopy of electron-ion wave packets in Rydberg N<inf>2</inf>

Fushitani M., Toida Y., Légaré F., Hishikawa A.

Optics InfoBase Conference Papers 2014年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：Optics InfoBase Conference Papers

Time-resolved photoelectron spectroscopy of N2 Rydberg using single-order high harmonics at 80 nm reveals ultrafast wavepacket dynamics (~3 fs) of both Rydberg electron and the corresponding N2 + core as the beating oscillation (~ 300 fs). © 2014 OSA.

DOI： 10.1364/up.2014.07.mon.p1.5

Ultrafast coulomb explosion of formaldehyde in 7 and 35 fs intense laser fields studied by triple ion-coincidence momentum imaging

Tseng C.M., Matsuda A., Fushitani M., Hishikawa A.

Optics InfoBase Conference Papers 2014年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：Optics InfoBase Conference Papers

Ultrafast three-body Coulomb explosion of formaldehyde (H2CO) in intense laser fields has been studied. The pulse duration dependence of the Newton plot of the fragment ions revealed the ultrafast molecular dynamics in the dication states. © 2014 OSA.

DOI： 10.1364/up.2014.09.wed.p3.23

Two-photon rabi oscillations of excited he atoms in ultrafast strong laser field ionization

Fushitani M., Liu C.N., Matsuda A., Endo T., Toida Y., Hikosaka Y., Nagasono M., Togashi T., Yabashi M., Ishikawa T., Morishita T., Hishikawa A.

Optics InfoBase Conference Papers 2014年

Time-resolved Coulomb explosion imaging of ultrafast fragmentation of CS<inf>2</inf> in highly charged states

Matsuda A., Takahashi E.J., Hishikawa A.

Optics InfoBase Conference Papers 2014年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：Optics InfoBase Conference Papers

Time-resolved Coulomb explosion imaging of CS2 in few-cycle intense laser fields revealed that the ultrafast fragmentation dynamics of CS2 in highly charged states proceed in a different timescale depending on the charge state. © 2014 OSA.

DOI： 10.1364/up.2014.08.tue.p2.18

Nonresonant EUV-UV two-color two-photon ionization of He studied by single-shot photoelectron spectroscopy 査読有り

Fushitani, M; Hikosaka, Y; Matsuda, A; Endo, T; Shigemasa, E; Nagasono, M; Sato, T; Togashi, T; Yabashi, M; Ishikawa, T; Hishikawa, A

PHYSICAL REVIEW A 88 巻 ( 6 ) 頁： 063422 2013年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physical Review A - Atomic, Molecular, and Optical Physics

Single-shot photoelectron spectroscopy of nonresonant two-color two-photon ionization of He has been carried out using an intense free-electron laser (FEL) at 59.7 nm and a femtosecond UV laser at 268 nm. By shot-by-shot analysis of photoelectron spectra, the cross section for nonresonant two-color ionization of He is determined to be σ(2)=4.1(6)×10-52 cm4 s. The cross-correlation trace derived from the nonresonant signals shows that the temporal resolution of the system is 0.36(3) ps, which is mainly governed by the timing jitter between the FEL and UV laser pulses. © 2013 American Physical Society.

DOI： 10.1103/PhysRevA.88.063422

Compact XFEL and AMO sciences: SACLA and SCSS 査読有り

Yabashi, M; Tanaka, H; Tanaka, T; Tomizawa, H; Togashi, T; Nagasono, M; Ishikawa, T; Harries, JR; Hikosaka, Y; Hishikawa, A; Nagaya, K; Saito, N; Shigemasa, E; Yamanouchi, K; Ueda, K

JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS 46 巻 ( 16 ) 頁： 164001 2013年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Physics B: Atomic, Molecular and Optical Physics

The concept, design and performance of Japan's compact free-electron laser (FEL) facilities, the SPring-8 Compact SASE Source test accelerator (SCSS) and SPring-8 Angstrom Compact free electron LAser (SACLA), and their applications in mainly atomic, molecular and optical science are reviewed. At SCSS, intense, ultrafast FEL pulses at extreme ultraviolet (EUV) wavelengths have been utilized for investigating various multi-photon processes in atoms, molecules and clusters by means of ion and electron spectroscopy. The quantum optical effect superfluorescence has been observed with EUV excitation. A pump-probe technique combining FEL pulses with near infrared laser pulses has been realized to study the ultrafast dynamics of atoms, molecules and clusters in the sub-picosecond regime. At SACLA, deep inner-shell multi-photon ionization by intense x-ray FEL pulses has been investigated. The development of seeded FEL sources for producing transversely and temporally coherent light, as well as the expected impact on advanced science are discussed. © 2013 IOP Publishing Ltd.

DOI： 10.1088/0953-4075/46/16/164001

Resonances in three-photon double ionization of Ar in intense extreme ultraviolet free-electron laser fields studied by shot-by-shot photoelectron spectroscopy 査読有り

Y. Hikosaka, M. Fushitani, A. Matsuda, T. Endo, Y. Toida, E. Shigemasa, M. Nagasono, K. Tono, T. Togashi, M. Yabashi, T. Ishikawa and A. Hishikawa

Phys. Rev. A 88 巻 ( 023421 ) 頁： 023421 2013年8月

Resonances in three-photon double ionization of Ar in intense extreme-ultraviolet free-electron laser fields studied by shot-by-shot photoelectron spectroscopy 査読有り

Hikosaka, Y; Fushitani, M; Matsuda, A; Endo, T; Toida, Y; Shigemasa, E; Nagasono, M; Tono, K; Togashi, T; Yabashi, M; Ishikawa, T; Hishikawa, A

PHYSICAL REVIEW A 88 巻 ( 2 ) 2013年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physical Review A - Atomic, Molecular, and Optical Physics

Shot-by-shot photoelectron spectroscopy has been performed to study the three-photon double ionization of Ar in intense extreme-ultraviolet free-electron laser fields over a photon energy range of 19.6-22.0 eV. It is found that the double ionization to Ar2+ 3p-2 proceeds sequentially via the formation of singly charged Ar+ 3p-1 states and is enhanced around photon energies of 20.5 and 21.5 eV. Two types of resonance are identified in the two-photon ionization of the Ar+ 3p-1 states: (i) resonances to intermediate states at the one-photon energy level and (ii) those to autoionizing states above the Ar+ ionization threshold. © 2013 American Physical Society.

DOI： 10.1103/PhysRevA.88.023421

Time-resolved Four-body Coulomb Explosion Imaging of Correlated Dynamics of Hydrogen Atoms in Acetylene Dication 査読有り Open Access

Matsuda, A; Fushitani, M; Takahashi, EJ; Hishikawa, A

XVIIITH INTERNATIONAL CONFERENCE ON ULTRAFAST PHENOMENA 41 巻 2013年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：EPJ Web of Conferences

The correlated motion of the two deuterium atoms associated with the hydrogen migration and structural deformation to non-planar geometry are identified in acetylene dication by the time-resolved four-body Coulomb explosion imaging. © Owned by the authors, published by EDP Sciences, 2013.

DOI： 10.1051/epjconf/20134102013

Ultrafast Nonlinear Double Excitations of He in Intense EUV FEL Fields 査読有り Open Access

Fushitani, M; Hikosaka, Y; Matsuda, A; Liu, CN; Morishita, T; Shigemasa, E; Hishikawa, A

XVIIITH INTERNATIONAL CONFERENCE ON ULTRAFAST PHENOMENA 41 巻 2013年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：EPJ Web of Conferences

Three-photon double excitation of He in intense EUV FEL fields is studied by the shot-by-shot photoelectron spectroscopy, revealing the enhancement by resonances to the doubly excited states converging to the He+ N=3 level. © Owned by the authors, published by EDP Sciences, 2013.

DOI： 10.1051/epjconf/20134102009

Shot-by-Shot Photoelectron Spectroscopy of Rare Gas Atoms in Ultrashort Intense EUV Free-Electron Laser Fields

Mizuho Fushitani, Yasumasa Hikosaka, Akitaka Matsuda, Eiji Shigemasa, Akiyoshi Hishikawa

Springer Series in Chemical Physics 頁： 151 - 163 2013年

Two-electron dynamics in nonlinear double excitation of helium by intense ultrashort extreme-ultraviolet pulses 査読有り

Liu, CN; Hishikawa, A; Morishita, T

PHYSICAL REVIEW A 86 巻 ( 5 ) 頁： 13 2012年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physical Review A - Atomic, Molecular, and Optical Physics

We present a theoretical study for multiphoton double excitation of He atoms exposed to an intense ultrashort extreme-ultraviolet (EUV) pulse, where the photon energy coincides with the transition energy from the ground state to a Rydberg state, by solving the time-dependent Schrödinger equation in the hyperspherical coordinates. Photoelectron spectra under the conditions comparable with a recent experiment [Hishikawa, Phys. Rev. Lett.PRLTAO0031- 900710.1103/PhysRevLett.107.243003 107, 243003 (2011)] are calculated and analyzed. We identify the mechanism of the enhanced three-photon absorption probability which is more than one order of magnitude larger than that for the two-photon process in accordance with the experiment. The enhancement is attributed to a propensity rule for double excitation in a two-step mechanism, in which a one-photon absorption by one electron to a Rydberg state is followed by a two-photon absorption by the other electron to an excited orbital, while the first electron remains at nearly the same principle quantum number. Based on the time-dependent perturbation theory, the three-photon absorption probability exhibits peculiar cubic dependence on the pulse duration due to the propensity rule, in contrast to the linear dependence of the two-photon absorption probability. Thus a crossover between the two- and three-photon absorption probabilities takes place for sufficiently intense and long pulses. We also study the time evolution of a doubly excited two-electron wave packet created by an intense ultrashort EUV pulse efficiently using the same enhancement scheme, opening up the possibility of visualizing the correlated motion of two electrons in the time domain. © 2012 American Physical Society.

DOI： 10.1103/PhysRevA.86.053426

レーザークーロン爆発イメージングによる実時間反応追跡招待有り査読有り

菱川明栄

レーザー研究 40 巻頁： 745-751 2012年10月

EUV and soft X-ray photoelectron spectroscopy of isolated atoms and molecules using single-order laser high-harmonics at 42 eV and 91 eV 査読有り

M. Fushitani, A. Matsuda and A. Hishikawa

J. Electron. Spectrosc. Relat. Phenom. 184 巻頁： 561-568 2012年2月

極紫外自由電子レーザー場における原子のシングルショット光電子分光招待有り査読有り

彦坂泰正，伏谷瑞穂，菱川明栄

しょうとつ 9 巻 ( 1 ) 頁： 5-10 2012年1月

EUV and soft X-ray photoelectron spectroscopy of isolated atoms and molecules using single-order laser high-harmonics at 42 eV and 91 eV 査読有り

Fushitani, M; Matsuda, A; Hishikawa, A

JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA 184 巻 ( 11-12 ) 頁： 561 - 568 2012年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Electron Spectroscopy and Related Phenomena

Photoelectron spectroscopy of isolated atoms and molecules using single-order high-harmonics of Ti:Sapphire laser pulses (800 nm, 12 fs/30 fs) is demonstrated. Dielectric multilayer mirrors, SiC/Mg and Mo/Si, are used to isolate the 27th (42 eV) and 59th (91 eV) order harmonics, respectively. The obtained harmonics are characterized by valence and inner-shell photoelectron spectroscopy of Xe. The applications to two-color two-photon ionization of He and pump-probe spectroscopy of ultrafast photodissociation of Br 2, Br 2(C 1Π u) → Br( 2P 3/2) + Br( 2P 3/2), are presented. © 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.elspec.2011.10.002

Theoretical study of multi-photon double electron excitation of He by intense ultrashort EUV pulses 査読有り

Liu Chien-Nan, Morishita Toru, Watanabe Shinichi, Hishikawa Akiyoshi

XXVII INTERNATIONAL CONFERENCE ON PHOTONIC, ELECTRONIC AND ATOMIC COLLISIONS (ICPEAC 2011), PTS 1-15 388 巻 ( PART 3 ) 2012年

記述言語：日本語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：Journal of Physics: Conference Series

We use the time-dependent hypersperhical close-coupling method to study the double excitation of helium atoms by intense ultrashort XUV pulses. In addition to showing the photoelectron yield spectra, we demonstrate that free electron lasers can be used to efficiently create doubly excited electron wave packets, opening up the possibility of visualizing the correlated motion of electrons in atoms. © Published under licence by IOP Publishing Ltd.

DOI： 10.1088/1742-6596/388/3/032007

Visualizing correlated dynamics of hydrogen atoms in acetylene dication by time-resolved four-body coulomb explosion imaging 査読有り

Matsuda A., Fushitani M., Takahashi E., Hishikawa A.

Springer Proceedings in Physics 125 巻頁： 317 - 322 2012年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：Springer Proceedings in Physics

Ultrafast hydrogenmigration in deuterated acetylene dication (C 2D2+2 ) is studied by time-resolved four-body Coulomb explosion imaging, C2D4+2 → D++ C ++ C ++ D +, using a pair of few-cycle intense laser pulses (9 fs, 1.3 × 1014 W/cm 2). Momentum correlation of the D+ ions produced by the full fragmentation process shows that (1) motions of the two deuterium atoms are strongly correlated during the isomerization and (2) the molecular structure deforms to nonplanar geometries. © Springer-Verlag Berlin Heidelberg 2012.

DOI： 10.1007/978-3-642-28948-4_53

Enhanced Nonlinear Double Excitation of He in Intense Extreme Ultraviolet Laser Fields 査読有り

Hishikawa, A; Fushitani, M; Hikosaka, Y; Matsuda, A; Liu, CN; Morishita, T; Shigemasa, E; Nagasono, M; Tono, K; Togashi, T; Ohashi, H; Kimura, H; Senba, Y; Yabashi, M; Ishikawa, T

PHYSICAL REVIEW LETTERS 107 巻 ( 24 ) 頁： 243003 2011年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physical Review Letters

Nonlinear, three-photon double excitation of He in intense extreme ultraviolet free-electron laser fields (∼24.1eV, ∼5TW/cm,sup>2) is presented. Resonances to the doubly excited states converging to the He + N=3 level are revealed by the shot-by-shot photoelectron spectroscopy and identified by theoretical calculations based on the time-dependent Schrödinger equation for the two-electron atom under a laser field. It is shown that the three-photon double excitation is enhanced by intermediate Rydberg states below the first ionization threshold, giving a greater contribution to the photoionization yields than the two-photon process by more than 1 order of magnitude. © 2011 American Physical Society.

DOI： 10.1103/PhysRevLett.107.243003

クーロン爆発イメージングによる超高速反応追跡招待有り

菱川明栄

光アライアンス 22 巻 ( 11 ) 頁： 19-22 2011年11月

光のゆらぎで探る：自由電子レーザー場中の原子招待有り

伏谷瑞穂, 彦坂泰正, 菱川明栄

光アライアンス 22 巻 ( 10 ) 頁： 25-28 2011年10月

A magnetic-bottle multi-electron-ion coincidence spectrometer 査読有り

Matsuda, A; Fushitani, M; Tseng, CM; Hikosaka, Y; Eland, JHD; Hishikawa, A

REVIEW OF SCIENTIFIC INSTRUMENTS 82 巻 ( 10 ) 頁： 103105 2011年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Review of Scientific Instruments

A novel multi-electron-ion coincidence spectrometer developed on the basis of a 1.5 m-long magnetic-bottle electron spectrometer is presented. Electrons are guided by an inhomogeneous magnetic field to a detector at the end of the flight tube, while a set of optics is used to extract counterpart ions to the same detector, by a pulsed inhomogeneous electric field. This setup allows ion detection with high mass resolution, without impairing the high collection efficiency for electrons. The performance of the coincidence spectrometer was tested with double ionization of carbon disulfide, CS2 → CS 22+e-e-, in ultrashort intense laser fields (2.8 × 1013W/cm2, 280 fs, 1030 nm) to clarify the electron correlation below the rescattering threshold. © 2011 American Institute of Physics.

DOI： 10.1063/1.3648133

Time-resolved EUV photoelectron spectroscopy of dissociating I<sub>2</sub> by laser harmonics at 80 nm 査読有り Open Access

Fushitani, M; Matsuda, A; Hishikawa, A

OPTICS EXPRESS 19 巻 ( 10 ) 頁： 9600 - 9606 2011年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Optics Express

Generation of single-order laser harmonics in extreme ultraviolet (EUV) and the application to the time-resolved photoelectron spectroscopy of I 2 are demonstrated. The EUV pulses at 80 nm were generated from Kr as the 5th order harmonics of intense 400 nm laser pulses and then separated from other harmonic orders by a thin indium foil. The pump-probe photoelectron spectroscopy of I2 in the B 3Π(0u+) and B" 1Π(1u) states excited by visible laser pulses at 490 nm showed a rapid increase in the yield of atomic iodine (∼400 fs), reflecting the dissociation dynamics evolving simultaneously in the two excited states. © 2011 Optical Society of America.

DOI： 10.1364/OE.19.009600

Time-resolved EUV photoelectron spectroscopy of dissociating I(2) by laser harmonics at 80 nm 査読有り

Fushitani, M. and Matsuda, A. and Hishikawa, A.

Optics Express 19 巻 ( 10 ) 頁： 9600-9606 2011年

記述言語：英語掲載種別：研究論文（学術雑誌）

Generation of single-order laser harmonics in extreme ultraviolet (EUV) and the application to the time-resolved photoelectron spectroscopy of I(2) are demonstrated. The EUV pulses at 80 nm were generated from Kr as the 5th order harmonics of intense 400 nm laser pulses and then separated from other harmonic orders by a thin indium foil. The pump-probe photoelectron spectroscopy of I(2) in the B (3)Pi(0(u)(+)) and B" (1)Pi(1(u)) states excited by visible laser pulses at 490 nm showed a rapid increase in the yield of atomic iodine (similar to 400 fs), reflecting the dissociation dynamics evolving simultaneously in the two excited states. (C) 2011 Optical Society of America

Visualizing hydrogen atoms migrating in acetylene dication by time-resolved three-body and four-body Coulomb explosion imaging 査読有り

Matsuda, A. and Fushitani, M. and Takahashi, E. J. and Hishikawa, A.

Physical Chemistry Chemical Physics 13 巻 ( 19 ) 頁： 8697-8704 2011年

記述言語：英語掲載種別：研究論文（学術雑誌）

The visualization of ultrafast isomerization of deuterated acetylene dication (C(2)D(2)(2+)) is demonstrated by time-resolved Coulomb explosion imaging with sub-10 fs intense laser pulses ( 9 fs, 0.13 PW cm(-2), 800 nm). The Coulomb explosion imaging monitoring the three-body explosion process, C(2)D(2)(3+) -> D(+) + C(+) + CD(+), as a function of the delay between the pump and probe pulses revealed that the migration of a deuterium atom proceeds in a recurrent manner; One of the deuterium atoms first shifts from one carbon site to the other in a short timescale (similar to 90 fs), and then migrates back to the original carbon site by 280 fs, in competition with the molecular dissociation. Correlated motion of the two deuterium atoms associated with the hydrogen migration and structural deformation to non-planar geometry are identified by the time-resolved four-body Coulomb explosion imaging, C(2)D(2)(4+) - D(+) + C(+) + C(+) + D(+).

DOI： Doi 10.1039/C0cp02333g

Visualizing hydrogen atoms migrating in acetylene dication by time-resolved three-body and four-body Coulomb explosion imaging 査読有り

Matsuda, A; Fushitani, M; Takahashi, EJ; Hishikawa, A

PHYSICAL CHEMISTRY CHEMICAL PHYSICS 13 巻 ( 19 ) 頁： 8697 - 8704 2011年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physical Chemistry Chemical Physics

The visualization of ultrafast isomerization of deuterated acetylene dication (C2D22+) is demonstrated by time-resolved Coulomb explosion imaging with sub-10 fs intense laser pulses (9 fs, 0.13 PW cm-2, 800 nm). The Coulomb explosion imaging monitoring the three-body explosion process, C2D23+ → D+ + C+ + CD+, as a function of the delay between the pump and probe pulses revealed that the migration of a deuterium atom proceeds in a recurrent manner; One of the deuterium atoms first shifts from one carbon site to the other in a short timescale (∼90 fs), and then migrates back to the original carbon site by 280 fs, in competition with the molecular dissociation. Correlated motion of the two deuterium atoms associated with the hydrogen migration and structural deformation to non-planar geometry are identified by the time-resolved four-body Coulomb explosion imaging, C 2D24+ → D+ + C+ + C+ + D+. © 2011 the Owner Societies.

DOI： 10.1039/c0cp02333g

EUV SASE-FELを用いた原子の多光子多重イオン化過程の研究招待有り査読有り

彦坂泰正, 伏谷瑞穂, 菱川明栄

放射光 23 巻 ( 5 ) 頁： 291-294 2010年9月

Multiphoton Double Ionization of Ar in Intense Extreme Ultraviolet Laser Fields Studied by Shot-by-Shot Photoelectron Spectroscopy 査読有り

Hikosaka, Y; Fushitani, M; Matsuda, A; Tseng, CM; Hishikawa, A; Shigemasa, E; Nagasono, M; Tono, K; Togashi, T; Ohashi, H; Kimura, H; Senba, Y; Yabashi, M; Ishikawa, T

PHYSICAL REVIEW LETTERS 105 巻 ( 13 ) 2010年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physical Review Letters

Photoelectron spectroscopy has been performed to study the multiphoton double ionization of Ar in an intense extreme ultraviolet laser field (hν∼21eV, ∼5TW/cm2), by using a free electron laser (FEL). Three distinct peaks identified in the observed photoelectron spectra clearly show that the double ionization proceeds sequentially via the formation of Ar +: Ar+hν→Ar++e- and Ar ++2hν→Ar2++e-. Shot-by-shot recording of the photoelectron spectra allows simultaneous monitoring of FEL spectrum and the multiphoton process for each FEL pulse, revealing that the two-photon ionization from Ar+ is significantly enhanced by intermediate resonances in Ar+. © 2010 The American Physical Society.

DOI： 10.1103/PhysRevLett.105.133001

Multiphoton Double Ionization of Ar in Intense Extreme Ultraviolet Laser Fields Studied by Shot-by-Shot Photoelectron Spectroscopy 査読有り

Hikosaka, Y. and Fushitani, M. and Matsuda, A. and Tseng, C. M. and Hishikawa, A. and Shigemasa, E. and Nagasono, M. and Tono, K. and Togashi, T. and Ohashi, H. and Kimura, H. and Senba, Y. and Yabashi, M. and Ishikawa, T.

Physical Review Letters 105 巻 ( 13 ) 頁： 133001 2010年

記述言語：英語掲載種別：研究論文（学術雑誌）

Photoelectron spectroscopy has been performed to study the multiphoton double ionization of Ar in an intense extreme ultraviolet laser field (h nu similar to 21 eV, similar to 5 TW/cm(2)), by using a free electron laser (FEL). Three distinct peaks identified in the observed photoelectron spectra clearly show that the double ionization proceeds sequentially via the formation of Ar(+): Ar + h nu -> Ar(+) + e(-) and Ar(+) + 2h nu -> Ar(2+) + e(-). Shot-by-shot recording of the photoelectron spectra allows simultaneous monitoring of FEL spectrum and the multiphoton process for each FEL pulse, revealing that the two-photon ionization from Ar(+) is significantly enhanced by intermediate resonances in Ar(+).

DOI： Doi 10.1103/Physrevlett.105.133001

Multiple Explosion Pathways of the Deuterated Benzene Trication in 9-fs Intense Laser Fields 査読有り

Akitaka Matsuda, Mizuho Fushitani, Richard A. Thomas, Vitali Zhaunerchyk, Akiyoshi Hishikawa

JOURNAL OF PHYSICAL CHEMISTRY A 113 巻 ( 11 ) 頁： 2254 - 2260 2009年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

The fragmentation of deuterated benzene (CA) in ultrashort intense laser fields (9 fs, 1 x 10(15) W/cm(2)) is studied by the ion-coincidence momentum imaging technique. Five two-body and eight three-body Coulomb explosion pathways from the trication (C6D63+), associated with the deprotonation and ring-opening reactions, are identified. It is found from the fragment momentum correlation that all the observed three-body explosion processes proceed sequentially via the two-body Coulomb explosion forming molecular dications, CmDn2+, with (m,n) = (6,5), (5,5), (5,4), (4,4), (4,3), and (3,3), which further dissociate into pairs of monocations. The branching ratio of the fragmentation pathways estimated from the number of the observed coincidence events indicates that the fragmentation is nonstatistical.

DOI： 10.1021/jp806466x

Electron-ion coincidence momentum imaging of molecular dissociative ionization in intense laser fields: Application to CS2 査読有り

Akitaka Matsuda, Mizuho Fushitani, Akiyoshi Hishikawa

JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA 169 巻 ( 2-3 ) 頁： 97 - 101 2009年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER

An electron-ion coincidence momentum imaging apparatus has been developed and applied to dissociative ionization of CS2 in ultrashort intense laser fields. Photoelectron images of CS2 in 35 fs intense laser fields (2 x 10(13) W/cm(2), 800 nm, linearly polarized) recorded in coincidence with the parent ion, CS2+, show clear concentric ring patterns due to the above-threshold ionization (ATI) process. On the other hand, broad structureless distributions elongated along the direction of the laser polarization are observed in the coincidence electron images for the CS+ and S' fragment ions. The difference in the electron images indicates that the dissociative ionization does not proceed sequentially by the formation and photodissociation of CS2+ in intense laser fields. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.elspec.2008.12.004

Electron-ion coincidence momentum imaging of molecular dissociative ionization in intense laser fields: Application to CS(2) 査読有り

Matsuda, A. and Fushitani, M. and Hishikawa, A.

Journal of Electron Spectroscopy and Related Phenomena 169 巻 ( 2-3 ) 頁： 97-101 2009年

記述言語：英語掲載種別：研究論文（学術雑誌）

An electron-ion coincidence momentum imaging apparatus has been developed and applied to dissociative ionization of CS(2) in ultrashort intense laser fields. Photoelectron images of CS(2) in 35 fs intense laser fields (2 x 10(13) W/cm(2), 800 nm, linearly polarized) recorded in coincidence with the parent ion, CS(2)(+), show clear concentric ring patterns due to the above-threshold ionization (ATI) process. On the other hand, broad structureless distributions elongated along the direction of the laser polarization are observed in the coincidence electron images for the CS(+) and S' fragment ions. The difference in the electron images indicates that the dissociative ionization does not proceed sequentially by the formation and photodissociation of CS(2)(+) in intense laser fields. (C) 2008 Elsevier B.V. All rights reserved.

Multiple Explosion Pathways of the Deuterated Benzene Trication in 9-fs Intense Laser Fields 査読有り

Matsuda, A. and Fushitani, M. and Thomas, R. A. and Zhaunerchyk, V. and Hishikawa, A.

Journal of Physical Chemistry A 113 巻 ( 11 ) 頁： 2254-2260 2009年

記述言語：英語掲載種別：研究論文（学術雑誌）

The fragmentation of deuterated benzene (CA) in ultrashort intense laser fields (9 fs, 1 x 10(15) W/cm(2)) is studied by the ion-coincidence momentum imaging technique. Five two-body and eight three-body Coulomb explosion pathways from the trication (C(6)D(6)(3+)), associated with the deprotonation and ring-opening reactions, are identified. It is found from the fragment momentum correlation that all the observed three-body explosion processes proceed sequentially via the two-body Coulomb explosion forming molecular dications, C(m)D(n)(2+), with (m,n) = (6,5), (5,5), (5,4), (4,4), (4,3), and (3,3), which further dissociate into pairs of monocations. The branching ratio of the fragmentation pathways estimated from the number of the observed coincidence events indicates that the fragmentation is nonstatistical.

Time-resolved reaction imaging by intense few-cycle laser pulses and laser high-order harmonics 査読有り

M. Fushitani, A. Matsuda, E. J. Takahashi, A. Hishikawa

Journal of Physics: Conference Series 185 巻 2009年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：Institute of Physics Publishing

We discuss two novel approaches to visualize ultrafast dynamics of polyatomic molecules using few-cycle intense laser pulses and the high-order harmonics in the soft X-ray region, respectively. First, we present the real-time Coulomb explosion imaging of ultrafast isomerization of C 2D2 2+ by using intense few-cycle laser pulses (&lt
10 fs, ∼1 PW/cm2, ∼800 nm) to show that the hydrogen migration proceeds recurrently in competition with the molecular dissociation. Secondly, we present a new experimental setup for the real-time inner-core excitation imaging, focusing on the generation and separation of the light source using the 59th order harmonic pulses (∼91 eV) and their characteristics. © 2009 IOP Publishing Ltd.

DOI： 10.1088/1742-6596/185/1/012009

Acetylene-vinylidene isomerization in ultrashort intense laser fields studied by triple ion-coincidence momentum imaging 査読有り

Akiyoshi Hishikawa, Akitaka Matsuda, Eiji J. Takahashi, Mizuho Fushitani

JOURNAL OF CHEMICAL PHYSICS 128 巻 ( 8 ) 2008年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER INST PHYSICS

The isomerization of acetylene via hydrogen migration in intense laser fields (8 X 10 14 W/cm(2)) has been investigated by coincidence momentum imaging of the three-body Coulomb explosion process, C(2)H(2)(3+)-> H(+)C(+)CH(+). When ultrashort (9 fs) laser pulses are used, the angle between the momenta of C(+) and H(+) fragments exhibits a sharp distribution peaked at a small angle (similar to 20 degrees), showing that the hydrogen atom remains near the original carbon site in the acetylene configuration. On the other hand, a significantly broad distribution extending to larger momentum angles (similar to 120 degrees) is observed when the pulse duration is increased to 35 fs, indicating that the ultrafast isomerization to vinylidene is induced in the longer laser pulse, (c) 2008 American Institute of Physics.

DOI： 10.1063/1.2828557

Acetylene-vinylidene isomerization in ultrashort intense laser fields studied by triple ion-coincidence momentum imaging 査読有り

Hishikawa, A. and Matsuda, A. and Takahashi, E. J. and Fushitani, M.

Journal of Chemical Physics 128 巻 ( 8 ) 頁： 084302 2008年

記述言語：英語掲載種別：研究論文（学術雑誌）

The isomerization of acetylene via hydrogen migration in intense laser fields (8 X 10 14 W/cm(2)) has been investigated by coincidence momentum imaging of the three-body Coulomb explosion process, C(2)H(2)(3+)-> H(+)C(+)CH(+). When ultrashort (9 fs) laser pulses are used, the angle between the momenta of C(+) and H(+) fragments exhibits a sharp distribution peaked at a small angle (similar to 20 degrees), showing that the hydrogen atom remains near the original carbon site in the acetylene configuration. On the other hand, a significantly broad distribution extending to larger momentum angles (similar to 120 degrees) is observed when the pulse duration is increased to 35 fs, indicating that the ultrafast isomerization to vinylidene is induced in the longer laser pulse, (c) 2008 American Institute of Physics.

DOI： Doi 10.1063/1.2828557

Visualizing recurrently migrating hydrogen in acetylene dication by intense ultrashort laser pulses 査読有り

Akiyoshi Hishikawa, Akitaka Matsuda, Mizuho Fushitani, Eiji J. Takahashi

PHYSICAL REVIEW LETTERS 99 巻 ( 25 ) 2007年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

We demonstrate the visualization of ultrafast hydrogen migration in deuterated acetylene dication (C(2)D(2)(2+)) by employing the pump-probe Coulomb explosion imaging with sub-10-fs intense laser pulses (9 fs, 0.13 PW/cm(2), 800 nm). It is shown, from the temporal evolution of the momenta of the fragment ions produced by the three-body explosion, C(2)D(2)(3+) -> D(+)+C(+)+CD(+), that the migration proceeds in a recurrent manner: The deuterium atom first shifts from one carbon site to the other in a short time scale (similar to 90 fs) and then migrates back to the original carbon site by 280 fs, in competition with the molecular dissociation.

DOI： 10.1103/PhysRevLett.99.258302

Dalitz plot analysis of Coulomb exploding O-3 in ultrashort intense laser fields 査読有り

Akitaka Matsuda, Eiji J. Takahashi, Akiyoshi Hishikawa

JOURNAL OF CHEMICAL PHYSICS 127 巻 ( 11 ) 2007年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER INST PHYSICS

The three-body Coulomb explosion of O-3, O-3(3+)-> O++O++O+, in ultrashort intense laser fields (2x10(15) W/cm(2)) is studied with two different pulse durations (9 and 40 fs) by the coincidence momentum imaging method. In addition to a decrease in the total kinetic energy release, a broadening in the Dalitz plot distribution [Philos. Mag. 44, 1068 (1953)] is observed when the pulse duration is increased from 9 to 40 fs. The analysis based on a simple Coulomb explosion model shows that the geometrical structure of O-3 remains almost unchanged during the interaction with the few-cycle intense laser fields, while a significant structural deformation along all the three vibrational coordinates, including the antisymmetric stretching coordinate, is identified in the 40 fs intense laser fields. The observed nuclear dynamics are discussed in terms of the population transfer to the excited states of O-3. (c) 2007 American Institute of Physics.

DOI： 10.1063/1.2766718

Electronic and nuclear responses of fixed-in-space H2S to ultrashort intense laser fields (vol 97, art no 243002, 2006) 査読有り

Akiyoshi Hishikawa, Eiji J. Takahashi, Akitaka Matsuda

PHYSICAL REVIEW LETTERS 98 巻 ( 1 ) 2007年1月

Visualizing recurrently migrating hydrogen in acetylene dication by intense ultrashort laser pulses 査読有り

Hishikawa, A. and Matsuda, A. and Fushitani, M. and Takahashi, E. J.

Physical Review Letters 99 巻 ( 25 ) 頁： 258302 2007年

記述言語：英語掲載種別：研究論文（学術雑誌）

We demonstrate the visualization of ultrafast hydrogen migration in deuterated acetylene dication (C(2)D(2)(2+)) by employing the pump-probe Coulomb explosion imaging with sub-10-fs intense laser pulses (9 fs, 0.13 PW/cm(2), 800 nm). It is shown, from the temporal evolution of the momenta of the fragment ions produced by the three-body explosion, C(2)D(2)(3+) -> D(+)+C(+)+CD(+), that the migration proceeds in a recurrent manner: The deuterium atom first shifts from one carbon site to the other in a short time scale (similar to 90 fs) and then migrates back to the original carbon site by 280 fs, in competition with the molecular dissociation.

DOI： Doi 10.1103/Physrevlett.99.258302

Dalitz plot analysis of Coulomb exploding O-3 in ultrashort intense laser fields 査読有り

Matsuda, A. and Takahashi, E. J. and Hishikawa, A.

Journal of Chemical Physics 127 巻 ( 11 ) 頁： 114318 2007年

記述言語：英語掲載種別：研究論文（学術雑誌）

The three-body Coulomb explosion of O-3, O-3(3+)-> O++O++O+, in ultrashort intense laser fields (2x10(15) W/cm(2)) is studied with two different pulse durations (9 and 40 fs) by the coincidence momentum imaging method. In addition to a decrease in the total kinetic energy release, a broadening in the Dalitz plot distribution [Philos. Mag. 44, 1068 (1953)] is observed when the pulse duration is increased from 9 to 40 fs. The analysis based on a simple Coulomb explosion model shows that the geometrical structure of O-3 remains almost unchanged during the interaction with the few-cycle intense laser fields, while a significant structural deformation along all the three vibrational coordinates, including the antisymmetric stretching coordinate, is identified in the 40 fs intense laser fields. The observed nuclear dynamics are discussed in terms of the population transfer to the excited states of O-3. (c) 2007 American Institute of Physics.

DOI： Doi 10.1063/1.2766718

Coincidence momentum imaging of two- and three-body Coulomb explosion of ethanol in intense laser fields 査読有り

Ryuji Itakura, Takahiro Teramoto, Akiyoshi Hishikawa, Kaoru Yamanouchi

ULTRAFAST OPTICS V 132 巻頁： 375 - + 2007年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：SPRINGER

Dissociative ionization of ethanol in intense laser fields is investigated by the coincidence momentum imaging method. Two-body Coulomb explosion channels with the hydrogen migration are identified in addition to a three-body Coulomb explosion channel. On the basis of the momentum vector distributions of the fragment ions, the dissociative ionization dynamics is discussed.

DOI： 10.1007/978-0-387-49119-6_49

Coulomb explosion imaging of molecular dynamics in intense laser fields 査読有り

Akiyoshi Hishikawa, Kaoru Yamanouchi

Springer Series in Chemical Physics 85 巻頁： 1 - 24 2007年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

The nuclear dynamics of polyatomic molecules in intense laser fields (∼1 PW/cm2) is studied through the momentum imaging of the fragment ions produced through Coulomb explosion. Characteristic nuclear dynamics that occur on the multidimensional potential energy surfaces in intense laser fields, such as sequential and concerted bond-breaking and hydrogen migration, are elucidated from momentum correlations among the fragment ions. © 2007 Springer-Verlag.

DOI： 10.1007/978-3-540-38156-3-1

Visualizing recurrently migrating hydrogen by few-cycle intense laser pulses 査読有り

Akiyoshi Hishikawa, Akitaka Matsudal, Mizuho Fushitani, Eiji J. Takahashi

XXV INTERNATIONAL CONFERENCE ON PHOTONIC, ELECTRONIC AND ATOMIC COLLISIONS 88 巻頁： 12056 2007年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IOP PUBLISHING LTD

Ultrafast hydrogen migration in deuterated acetylene dication (C(2)D(2)(2+)) is studied by the pump-probe Coulomb explosion imaging with few-cycle intense laser pulses (9 fs, 0.13 PW/cm(2), 800 nm). The temporal evolution of the momenta of the fragment ions produced by the three-body explosion, C(2)D(2)(3+) -> D(+) + C(+) + CD(+), shows that the migration proceeds in a recurrent manner: The deuterium atom first shifts from one carbon site to the other in a short time scale (similar to 90 fs), and then migrates back to the original carbon site by 280 fs, in competition with the molecular dissociation.

DOI： 10.1088/1742-6596/88/1/012056

Visualizing recurrently migrating hydrogen by few-cycle intense laser pulses 査読有り

Akiyoshi Hishikawa, Akitaka Matsudal, Mizuho Fushitani, Eiji J. Takahashi

XXV INTERNATIONAL CONFERENCE ON PHOTONIC, ELECTRONIC AND ATOMIC COLLISIONS 88 巻 2007年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IOP PUBLISHING LTD

Ultrafast hydrogen migration in deuterated acetylene dication (C(2)D(2)(2+)) is studied by the pump-probe Coulomb explosion imaging with few-cycle intense laser pulses (9 fs, 0.13 PW/cm(2), 800 nm). The temporal evolution of the momenta of the fragment ions produced by the three-body explosion, C(2)D(2)(3+) -> D(+) + C(+) + CD(+), shows that the migration proceeds in a recurrent manner: The deuterium atom first shifts from one carbon site to the other in a short time scale (similar to 90 fs), and then migrates back to the original carbon site by 280 fs, in competition with the molecular dissociation.

DOI： 10.1088/1742-6596/88/1/012056

Electronic and nuclear responses of fixed-in-space H2S to ultrashort intense laser fields 査読有り

Akiyoshi Hishikawa, Eiji J. Takahashi, Akitaka Matsuda

PHYSICAL REVIEW LETTERS 97 巻 ( 24 ) 2006年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMERICAN PHYSICAL SOC

The Coulomb explosion dynamics of H2S, H2S3+-> H++S++H+, in ultrashort intense laser fields (12 fs, similar to 2x10(14) W/cm(2)) is studied by the coincidence momentum imaging of the three fragment ions. Different electronic and nuclear responses are identified depending on the direction of laser polarization epsilon in the molecular frame. The dependence can be interpreted in terms of the electronic and bonding characters of charge transfer states of H2S coupled to the electronic ground state.

DOI： 10.1103/PhysRevLett.97.243002

Dissociative ATI of H-2 and D-2 in intense soft x-ray laser fields 査読有り

K Hoshina, A Hishikawa, K Kato, T Sako, K Yamanouchi, EJ Takahashi, Y Nabekawa, K Midorikawa

JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS 39 巻 ( 4 ) 頁： 813 - 829 2006年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IOP PUBLISHING LTD

The dissociative photoionization processes of H-2 and D-2 in an intense, short-pulsed soft x-ray field (lambda = 29.6 nm, 3 x 10(12) W CM-2, 15 fs) generated as the 27th high-order harmonic of a Ti:sapphire laser is investigated for the first time by time-of-flight mass spectrometry. The ejected H+ fragment ions from H2 are distributed in the kinetic energy range of 3-20 eV peaked at 10.0 eV, and the yield exhibits a nonlinear dependence of the order of 1.7(l) on the light field intensity of the 27th harmonic. Similarly, the D+ fragment ions from D-2 are distributed in the 3-20 eV range peaked at 10.3 eV, and the yield exhibits a nonlinear dependence of the order of 1.6 +/- 0.2. The kinetic energy distributions of H+ and D+ and the nonlinearity in their yields are interpreted well by the two coexisting ionization processes: (i) one-photon dissociative ionization and (ii) dissociative two-photon above-threshold-ionization (ATI) mainly into the repulsive 2p pi(u) state.

DOI： 10.1088/0953-4075/39/4/007

Electronic and nuclear responses of fixed-in-space H2S to ultrashort intense laser fields 査読有り

Hishikawa, A. and Takahashi, E. J. and Matsuda, A.

Physical Review Letters 97 巻 ( 24 ) 頁： 243002 2006年

記述言語：英語掲載種別：研究論文（学術雑誌）

The Coulomb explosion dynamics of H2S, H2S3+-> H++S++H+, in ultrashort intense laser fields (12 fs, similar to 2x10(14) W/cm(2)) is studied by the coincidence momentum imaging of the three fragment ions. Different electronic and nuclear responses are identified depending on the direction of laser polarization epsilon in the molecular frame. The dependence can be interpreted in terms of the electronic and bonding characters of charge transfer states of H2S coupled to the electronic ground state.

DOI： Doi 10.1103/Physrevlett.97.243002

Dissociative ATI of H-2 and D-2 in intense soft x-ray laser fields 査読有り

Hoshina, K. and Hishikawa, A. and Kato, K. and Sako, T. and Yamanouchi, K. and Takahashi, E. J. and Nabekawa, Y. and Midorikawa, K.

Journal of Physics B-Atomic Molecular and Optical Physics 39 巻 ( 4 ) 頁： 813-829 2006年

記述言語：英語掲載種別：研究論文（学術雑誌）

The dissociative photoionization processes of H-2 and D-2 in an intense, short-pulsed soft x-ray field (lambda = 29.6 nm, 3 x 10(12) W CM-2, 15 fs) generated as the 27th high-order harmonic of a Ti:sapphire laser is investigated for the first time by time-of-flight mass spectrometry. The ejected H+ fragment ions from H2 are distributed in the kinetic energy range of 3-20 eV peaked at 10.0 eV, and the yield exhibits a nonlinear dependence of the order of 1.7(l) on the light field intensity of the 27th harmonic. Similarly, the D+ fragment ions from D-2 are distributed in the 3-20 eV range peaked at 10.3 eV, and the yield exhibits a nonlinear dependence of the order of 1.6 +/- 0.2. The kinetic energy distributions of H+ and D+ and the nonlinearity in their yields are interpreted well by the two coexisting ionization processes: (i) one-photon dissociative ionization and (ii) dissociative two-photon above-threshold-ionization (ATI) mainly into the repulsive 2p pi(u) state.

Concerted and sequential Coulomb explosion processes of N2O in intense laser fields by coincidence momentum imaging 査読有り

M Ueyama, H Hasegawa, A Hishikawa, K Yamanouchi

JOURNAL OF CHEMICAL PHYSICS 123 巻 ( 15 ) 2005年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER INST PHYSICS

The Coulomb explosion dynamics of N2O in intense laser fields (800 nm, 60 fs, similar to 0.16 PW/cm(2)) is studied by the coincidence momentum imaging method. From the momentum correlation maps obtained for the three-body fragmentation pathway, N2O3+-> N++N++O+, the ultrafast structural deformation dynamics of N2O prior to the Coulomb explosion is extracted. It is revealed that the internuclear N-N and N-O distances stretch simultaneously as the bond angle > N-N-O decreases. In addition, two curved thin distributions are identified in the momentum correlation maps, and are interpreted well as those originating from the sequential dissociation pathway, N2O3+-> N++NO2+-> N++N++O+. (c) 2005 American Institute of Physics.

DOI： 10.1063/1.2032988

Probing the ultrafast nuclear motion in CS22+ in intense laser fields 査読有り

A Hishikawa, M Ueyama, K Yamanouchi

JOURNAL OF CHEMICAL PHYSICS 122 巻 ( 15 ) 2005年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER INST PHYSICS

The temporal evolution of the nuclear wave packet of CS(2)2+ formed in an intense laser field (60 fs, 0.13 PW/cm(2)) is traced in real time by the pump-and-probe technique combined with coincidence momentum imaging of the Coulomb explosion process, CS23+->S+ + C+ + S+. The momentum correlations among the fragment ions obtained as a function of the pump-probe time delay between 133 fs to 3 ps reveal that the nuclear wave packet in CS22+ evolves not only along the anti-symmetric stretching coordinate to yield S+ and CS+ but also along the symmetric stretching coordinate leading to the simultaneous breaking of the two C-S bonds. The contribution from two different electronic states having bent and linear-type geometrical configurations is identified in the wave packet motion along the bending coordinate of CS22+. 2005 American Institute of Physics.

DOI： 10.1063/1.1895745

Probing the ultrafast nuclear motion in CS22+ in intense laser fields 査読有り

Hishikawa, A. and Ueyama, M. and Yamanouchi, K.

Journal of Chemical Physics 122 巻 ( 15 ) 頁： 151104 2005年

記述言語：英語掲載種別：研究論文（学術雑誌）

The temporal evolution of the nuclear wave packet of CS(2)2+ formed in an intense laser field (60 fs, 0.13 PW/cm(2)) is traced in real time by the pump-and-probe technique combined with coincidence momentum imaging of the Coulomb explosion process, CS23+->S+ + C+ + S+. The momentum correlations among the fragment ions obtained as a function of the pump-probe time delay between 133 fs to 3 ps reveal that the nuclear wave packet in CS22+ evolves not only along the anti-symmetric stretching coordinate to yield S+ and CS+ but also along the symmetric stretching coordinate leading to the simultaneous breaking of the two C-S bonds. The contribution from two different electronic states having bent and linear-type geometrical configurations is identified in the wave packet motion along the bending coordinate of CS22+. 2005 American Institute of Physics.

DOI： Doi 10.1063/1.1895745

Concerted and sequential Coulomb explosion processes of N2O in intense laser fields by coincidence momentum imaging 査読有り

Ueyama, M. and Hasegawa, H. and Hishikawa, A. and Yamanouchi, K.

Journal of Chemical Physics 123 巻 ( 15 ) 頁： 154305 2005年

記述言語：英語掲載種別：研究論文（学術雑誌）

The Coulomb explosion dynamics of N2O in intense laser fields (800 nm, 60 fs, similar to 0.16 PW/cm(2)) is studied by the coincidence momentum imaging method. From the momentum correlation maps obtained for the three-body fragmentation pathway, N2O3+-> N++N++O+, the ultrafast structural deformation dynamics of N2O prior to the Coulomb explosion is extracted. It is revealed that the internuclear N-N and N-O distances stretch simultaneously as the bond angle > N-N-O decreases. In addition, two curved thin distributions are identified in the momentum correlation maps, and are interpreted well as those originating from the sequential dissociation pathway, N2O3+-> N++NO2+-> N++N++O+. (c) 2005 American Institute of Physics.

DOI： Doi 10.1063/1.2032988

Hydrogen migration in acetonitrile in intense laser fields in competition with two-body Coulomb explosion 査読有り

A Hishikawa, H Hasegawa, K Yamanouchi

JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA 141 巻 ( 2-3 ) 頁： 195 - 200 2004年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

Two-body Coulomb explosion processes of acetonitrile (CH3CN) and deuterated acetonitrile (CD3CN), CH3CN2+ --> CH3-n+ +HnCN+ and CD3CN2+ --> CD3-n+ +DnCN+ (n = 0-2), in an intense laser field (0.15 pW/cm(2), 70 fs) are investigated by the coincidence momentum imaging method. The comparable yields derived for the three pathways (n = 0-2) shows that the hydrogen atom migration proceeds in competition with the Coulomb explosion. The angular distributions of the fragment ions for n = 0 exhibits a sharp peak along the laser polarization direction while the angular distribution becomes more isotropic as n increases. Based on a least-squares analysis of the fragment anisotropy, the dissociation lifetimes of the doubly charged acetonitrile were determined, from which the time scale of the hydrogen migration as well as the deformation of the C-C-N skeleton prior to the explosion were discussed. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.elspec.2004.06.009

Nuclear dynamics on the light-dressed potential energy surface Of CS2 by coincidence momentum imaging 査読有り

A Hishikawa, H Hasegawa, K Yamanouchi

CHEMICAL PHYSICS LETTERS 388 巻 ( 1-3 ) 頁： 1 - 6 2004年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

The non-sequential three-body Coulomb explosion, CS23+ --> S+ + C+ + S+, in an intense laser field (0.2 PW/cm(2), 60 fs) is studied by the coincidence momentum imaging of the fragment ions. The observed angular distribution of the momentum vectors of the two S+ ions, p(1) (S+) and p(2)(S+), exhibits a peak at an angle as small as theta(12) similar to 140degrees, showing that the nuclear motion is induced along the bending coordinate to a large extent prior to the explosion. On the other hand, the difference between their absolute values, Deltap(12) = \p(1)(S+)\ - \p(2)(S+), has a sharp distribution peaked at Deltap(12) = 0, suggesting that the symmetric stretching motion dominates over the antisymmetric stretching motion in the laser field. Based on the energy dependence of the momentum vector correlation, the characteristic nuclear dynamics of CS2 on the light-dressed potential energy surfaces in an intense laser field is discussed. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.cplett.2004.01.128

Hydrogen migration in acetonitrile in intense laser fields in competition with two-body Coulomb explosion 査読有り

Hishikawa, A. and Hasegawa, H. and Yamanouchi, K.

Journal of Electron Spectroscopy and Related Phenomena 141 巻 ( 2-3 ) 頁： 195-200 2004年

記述言語：英語掲載種別：研究論文（学術雑誌）

Two-body Coulomb explosion processes of acetonitrile (CH3CN) and deuterated acetonitrile (CD3CN), CH3CN2+ --> CH3-n+ +HnCN+ and CD3CN2+ --> CD3-n+ +DnCN+ (n = 0-2), in an intense laser field (0.15 pW/cm(2), 70 fs) are investigated by the coincidence momentum imaging method. The comparable yields derived for the three pathways (n = 0-2) shows that the hydrogen atom migration proceeds in competition with the Coulomb explosion. The angular distributions of the fragment ions for n = 0 exhibits a sharp peak along the laser polarization direction while the angular distribution becomes more isotropic as n increases. Based on a least-squares analysis of the fragment anisotropy, the dissociation lifetimes of the doubly charged acetonitrile were determined, from which the time scale of the hydrogen migration as well as the deformation of the C-C-N skeleton prior to the explosion were discussed. (C) 2004 Elsevier B.V. All rights reserved.

Hydrogen migration in acetonitrile in intense laser fields studied by coincidence momentum imaging 査読有り

Hishikawa, A. and Hasegawa, H. and Yamanouchi, K.

Physica Scripta T110 巻頁： 108-111 2004年

記述言語：英語掲載種別：研究論文（学術雑誌）

The two-body Coulomb explosion of acetonitrile, CH3CN2+ -> CH3-n+ + HnCN+(n = 0-2), in intense laser fields (0.15 PW/cm(2), 70 fs) is studied by the coincidence momentum imaging technique. It is found that the fragment ions for n 0 are ejected mostly in the direction of the laser polarization vector with < cos(2)theta > = 0.68, where theta is the angle between the fragment recoil direction and the laser polarization vector, while the angle distribution becomes more isotropic as n increases, i.e., < cos(2)theta > = 0.49 for n = 1 and < cos(2)theta > = 0.37 for n = 2. From this characteristic correlation between the anisotropy in the fragment ejection and the hydrogen migration, the Coulomb explosion dynamics competing with the hydrogen atom transfer from the methyl group to the nitrile group is investigated.

Nuclear dynamics on the light-dressed potential energy surface of CS2 by coincidence momentum imaging 査読有り

Hishikawa, A. and Hasegawa, H. and Yamanouchi, K.

Chemical Physics Letters 388 巻 ( 1-3 ) 頁： 1-6 2004年

記述言語：英語掲載種別：研究論文（学術雑誌）

The non-sequential three-body Coulomb explosion, CS23+ --> S+ + C+ + S+, in an intense laser field (0.2 PW/cm(2), 60 fs) is studied by the coincidence momentum imaging of the fragment ions. The observed angular distribution of the momentum vectors of the two S+ ions, p(1) (S+) and p(2)(S+), exhibits a peak at an angle as small as theta(12) similar to 140degrees, showing that the nuclear motion is induced along the bending coordinate to a large extent prior to the explosion. On the other hand, the difference between their absolute values, Deltap(12) = \p(1)(S+)\ - \p(2)(S+), has a sharp distribution peaked at Deltap(12) = 0, suggesting that the symmetric stretching motion dominates over the antisymmetric stretching motion in the laser field. Based on the energy dependence of the momentum vector correlation, the characteristic nuclear dynamics of CS2 on the light-dressed potential energy surfaces in an intense laser field is discussed. (C) 2004 Elsevier B.V. All rights reserved.

Hydrogen migration in acetonitrile in intense laser fields studied by coincidence momentum imaging 査読有り

Akiyoshi Hishikawa, Hirokazu Hasegawa, Kaoru Yamanouchi

PHYSICA SCRIPTA T110 巻頁： 108 - 111 2004年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IOP PUBLISHING LTD

The two-body Coulomb explosion of acetonitrile, CH3CN2+ -> CH3-n+ + HnCN+(n = 0-2), in intense laser fields (0.15 PW/cm(2), 70 fs) is studied by the coincidence momentum imaging technique. It is found that the fragment ions for n 0 are ejected mostly in the direction of the laser polarization vector with < cos(2)theta > = 0.68, where theta is the angle between the fragment recoil direction and the laser polarization vector, while the angle distribution becomes more isotropic as n increases, i.e., < cos(2)theta > = 0.49 for n = 1 and < cos(2)theta > = 0.37 for n = 2. From this characteristic correlation between the anisotropy in the fragment ejection and the hydrogen migration, the Coulomb explosion dynamics competing with the hydrogen atom transfer from the methyl group to the nitrile group is investigated.

DOI： 10.1238/Physica.Topical.110a00108

Hydrogen migration in acetonitrile in intense laser fields studied by coincidence momentum imaging 査読有り

Akiyoshi Hishikawa, Hirokazu Hasegawa, Kaoru Yamanouchi

Physica Scripta T T110 巻頁： 108 - 111 2004年

記述言語：英語掲載種別：研究論文（学術雑誌）

The two-body Coulomb explosion of acetonitrile, CH3CN 2+ → CH3-n+ + HnCN+ (n = 0-2), in intense laser fields (0.15 PW/cm2, 70 fs) is studied by the coincidence momentum imaging technique. It is found that the fragment ions for n = 0 are ejected mostly in the direction of the laser polarization vector with 〈 cos2 θ 〉 = 0.68, where θ is the angle between the fragment recoil direction and the laser polarization vector, while the angle distribution becomes more isotropic as n increases, i.e., 〈 cos2 θ 〉 = 0.49 for n = 1 and 〈 cos2 θ 〉 = 0.37 for n = 2. From this characteristic correlation between the anisotropy in the fragment ejection and the hydrogen migration, the Coulomb explosion dynamics competing with the hydrogen atom transfer from the methyl group to the nitrile group is investigated. © Physica Scripta 2004.

DOI： 10.1238/Physica.Topical.110a00108

Sequential three-body Coulomb explosion of CS2 in intense laser fields appearing in momentum correlation map 査読有り

A Hishikawa, H Hasegawa, K Yamanouchi

CHEMICAL PHYSICS LETTERS 361 巻 ( 3-4 ) 頁： 245 - 250 2002年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

The three-body Coulomb explosion process of CS2 in intense laser fields (60 fs, 0.36 x 10(15) W/cm(2)), CS23+ --> S+ + C+ + S+, is studied by the triple coincidence momentum imaging of the atomic fragment ions. The set of the observed momentum vectors of the fragment ions determined for respective explosion events exhibits a clear trajectory originating from the rotational motion of an intermediate CS2+ ion, formed in a sequential explosion process of CS23+ prior to the complete three-body fragmentation. The contribution of the sequential pathway to the overall three-body explosion process is estimated to be 17(1)%. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0009-2614(02)00880-1

Suppression of decomposition of aniline cation in intense laser fields by cluster formation with ammonia molecules 査読有り

J Watanabe, R Itakura, A Hishikawa, K Yamanouchi

JOURNAL OF CHEMICAL PHYSICS 116 巻 ( 22 ) 頁： 9697 - 9702 2002年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER INST PHYSICS

Mass-selected aniline cations and [aniline-(NH3)(n)](+) (n=1 and 2) cluster ions are exposed to the femtosecond laser fields (lambdasimilar to395 nm,Isimilar to4x10(15) W/cm(2)) and the nanosecond laser fields (lambda=532 nm,Isimilar to2.7x10(10) W/cm(2)) by using a tandem type time-of-flight mass spectrometer. In the case of the bare aniline cation, the decomposition forming the five-membered ring compound, cyclopentadienyl cation (C5H6+), dominantly proceeds in both the femtosecond and nanosecond laser fields. When one or two ammonia molecules are attached to the aniline cation, the decomposition is significantly suppressed. This suppression was interpreted in terms of an intermolecular energy flow through the hydrogen bonding. (C) 2002 American Institute of Physics.

DOI： 10.1063/1.1475753

Coincidence Imaging of coulomb explosion of CS2 in intense laser fields 査読有り

H Hasegawa, K Doi, A Hishikawa, K Yamanouchi

SCIENCE OF SUPERSTRONG FIELD INTERACTIONS 634 巻頁： 197 - 198 2002年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：AMER INST PHYSICS

The coincidence imaging technique is applied to direct determination of the momentum vectors of all the fragment ions produced through every event of the Coulomb explosion of a single molecular ion, CS2+ (z = 2 - 4) formed in intense laser fields (0.36 PW/cm(2)). The molecular structure Of CS23+ just before the three-body Coulomb explosion is reconstructed from the measured momentum vectors of the atomic fragment ions. It was confirmed that the skeletal deformation of CS2 is induced to a large extent in intense laser fields.

Coincidence imaging of Coulomb explosion of CS2 in intense laser fields 査読有り

H Hasegawa, A Hishikawa, K Yamanouchi

CHEMICAL PHYSICS LETTERS 349 巻 ( 1-2 ) 頁： 57 - 63 2001年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

The coincidence imaging technique is applied to direct determination of the momentum vectors of all the fragment ions produced through every event of the Coulomb explosion of a single molecular ion, CS22+ (z = 2-4) formed in intense laser of CS23+ just fields (similar to 60 fs, 0.36 x 10(15) W/cm(2)). The molecular structure I before the Coulomb explosion, CS23+ --> S+ + C+ + S+, is reconstructed from the measured momentum vectors of the fragment ions. The mean C-S bond length of <r > = 2.5 Angstrom and the azimuthally averaged S-C-S bond angle, < gamma > = 145 degrees, thus determined indicate that structural deformation occurs to a large extent in the intense laser fields. (C) 2001 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0009-2614(01)01087-9

Real-time probing of alignment and structural deformation of CS2 in intense nanosecond laser fields 査読有り

A Iwasaki, A Hishikawa, K Yamanouchi

CHEMICAL PHYSICS LETTERS 346 巻 ( 5-6 ) 頁： 379 - 386 2001年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

A time evolution of the alignment and structural deformation processes of neutral CS2 in intense non-resonant nanosecond laser fields (1.9 X 10(12) W/cm(2)) is derived by ionizing CS2 using intense circularly polarized feintosecond laser fields (5.5 x 10(14) W/cm(2)). From the real-time probing of the momentum distribution of the resultant S3+ and C2+ fragment ions produced through the Coulomb explosion induced by the intense fenitosecond laser fields, it is identified that the alignment and the structural deformation proceed simultaneously in the nanosecond laser fields. (C) 2001 Elsevier Science BN. All rights reserved.

DOI： 10.1016/S0009-2614(01)00963-0

Light-induced multiple electronic-state coupling of O-2(+) in intense laser fields 査読有り

A Hishikawa, SL Liu, A Iwasaki, K Yamanouchi

JOURNAL OF CHEMICAL PHYSICS 114 巻 ( 22 ) 頁： 9856 - 9862 2001年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER INST PHYSICS

The dissociation processes, O-2(+)-->O++O, in intense laser fields (100 fs, similar to 3x10(14) W/cm(2)) are studied at the laser wavelength of 795 and 398 nm on the basis of the momentum imaging maps of the O+ fragment ions. The covariance map measurements are performed with high momentum resolution to assign securely the dissociation pathways. From the anisotropic momentum distribution of O+ with respect to the laser polarization direction, the electronic states of O-2(+) are found to be coupled exclusively through parallel transitions in the course of the dissociation process. The released kinetic energy of O+ for both 795 and 398 nm are interpreted consistently by a sequential coupling model of light-dressed potential curves of O-2(+) in the quartet Pi state manifold. (C) 2001 American Institute of Physics.

DOI： 10.1063/1.1368383

Ionization and fragmentation dynamics of benzene in intense laser fields by tandem mass spectroscopy 査読有り

R Itakura, J Watanabe, A Hishikawa, K Yamanouchi

JOURNAL OF CHEMICAL PHYSICS 114 巻 ( 13 ) 頁： 5598 - 5606 2001年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER INST PHYSICS

Using a tandem time-of-flight mass spectrometer, benzene cations produced by the resonantly enhanced multiphoton ionization are mass separated and are exposed to intense laser fields (similar to 2x10(16) W/cm(2)) at lambda similar to 790 and 395 nm with the pulse duration of similar to 50 fs. Comparing the yields of the product ions with those obtained from neutral benzene molecules, the ionization and dissociation dynamics of benzene in intense laser fields is investigated. At lambda similar to 790 nm, the formation of parent benzene ions is a dominant process irrespective of the initial charge states, i.e., major products obtained when starting from neutral benzene are benzene cations and dications and those obtained when starting from benzene cation are benzene dications. On the other hand, at lambda similar to 395 nm, the fragmentation processes to produce C4Hi+(i=2-4) and C3Hj+(j=1-3) dominate over further ionization to the benzene dication for both cases starting from neutral benzene and benzene cation, indicating the population trapping occurs by the efficient confinement in the light-dressed mixture of the C and X states of benzene cations assisted by the ultrafast intramolecular decay process. (C) 2001 American Institute of Physics.

DOI： 10.1063/1.1352619

Resonance-state selective photodissociation of OCS (2(1)Sigma(+)): Rotational and vibrational distributions of CO fragments 査読有り

R Itakura, A Hishikawa, K Yamanouchi

JOURNAL OF CHEMICAL PHYSICS 113 巻 ( 16 ) 頁： 6598 - 6607 2000年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER INST PHYSICS

The rotational and vibrational state distributions of the CO fragments produced through the photodissociation of OCS in the vacuum ultraviolet (VUV) region (150-155 nm), OCS (2 (1)Sigma (+))--> CO (X (1)Sigma (+))+S(S-1), are derived for the three lowest quasi-bound vibrational resonances (upsilon*=0-2) in the 2 (1)Sigma (+) state. The rotational state distributions of the CO fragments in the upsilon (CO)=0 and 1 vibrational states are determined, respectively, by the analysis of the rotational structures in the laser-induced fluorescence (LIF) spectra of the A(1)Pi -X (1)Sigma (+)(0,0) and (1,1) transitions of CO. The rotational temperatures of CO in the upsilon (CO)=0 state are low (similar to 100 K) for all the three resonances, while those in the upsilon (CO)=1 state are substantially higher, i.e., 2210, 940, and 810 K for upsilon*=0, 1, and 2, respectively. The vibrational state distributions of CO are derived from the Doppler spectroscopy of the counterpart S(S-1) fragments. From the analysis of the observed Doppler profiles, it is found for all the three lowest vibrational resonances of OCS that the vibrational distributions are represented well by the Boltzmann-type distribution with a vibrational temperature of around 7000 K. On the basis of these new findings, the energy partitioning in the photodissociation process through these three vibrational resonances in the 2 (1)Sigma (+) state is discussed. (C) 2000 American Institute of Physics. [S0021-9606(00)01740-2].

DOI： 10.1063/1.1310606

Extraction of molecular dynamics in intense laser fields from mass-resolved momentum imaging maps: application to Coulomb explosion of NO 査読有り

A Iwamae, A Hishikawa, K Yamanouchi

JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS 33 巻 ( 2 ) 頁： 223 - 240 2000年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IOP PUBLISHING LTD

The nuclear dynamics of NO in intense laser fields (similar to 1.4 PW cm(-2)) is studied on the basis of the momentum-scaled time-of-flight spectra and mass-resolved momentum imaging maps of the atomic fragment ions, NP+ and Oq+ (p, q = 1-3), produced from the (p, q) Coulomb explosion pathways of NO, i.e. NO(p+q)+ --> Np+ + Oq+. A procedure to extract nuclear dynamics from the momentum maps is proposed by taking account of the effect of the finite detector size. The resultant nine (p, q) single-pathway components show that (a) the distributions of the N-O internuclear distance of NOz+ just before the Coulomb explosion exhibit significant broadening (similar to 1 Angstrom); (b) the distance at which the corresponding distribution takes a maximum increases from 1.68 to 2.34 Angstrom as z from 2 to 6 with a small amount of suppression at odd z (z = 3, 5); and (c) the atomic fragment ions exhibit narrower angular distributions for a larger total charge z (= p + q) of NOz+.

DOI： 10.1088/0953-4075/33/2/308

Ultrafast structural deformation of polyatomic molecules in intense laser fields 査読有り

K Yamanouchi, A Hishikawa, A Iwamae, SL Liu

PHYSICS OF ELECTRONIC AND ATOMIC COLLISIONS 500 巻頁： 182 - 191 2000年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：AMER INST PHYSICS

The momentum vector distributions of fragment ions produced through the Coulomb explosion of small molecules such as NO, CO2, NO2, and H2O in intense laser fields (similar to 1 PW/cm(2)) are measured by the mass-resolved momentum imaging (MRMI) technique. For NO, the MRMI maps for a single (p,q) pathway, NO(p+q)+ --> NP+ + Oq+ (p, q = 1 similar to 3), are extracted from the observed MRMI maps on the basis of the momentum matching of the NP+ and Oq+. ion pair. In the MRMI maps for the fragment ions produced from CO2, NO2, and H2O, their ultrafast structural deformation both along the stretching coordinate and along the bending coordinate is identified. The <O-C-O angle distribution of CO2 Spreads significantly (FWHM similar to 40 degrees), and the <O-N-O bond angle of NO2 increases toward a linear configuration within the ultrashort duration of the laser pulse. This type of deformation is also identified for H2O. These structural deformations are most reasonably interpreted as a consequence of the formation of light-dressed potential energy surfaces.

Ultrafast structural deformation of NO2 in intense laser fields studied by mass-resolved momentum imaging 査読有り

A Hishikawa, A Iwamae, K Yamanouchi

JOURNAL OF CHEMICAL PHYSICS 111 巻 ( 19 ) 頁： 8871 - 8878 1999年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER INST PHYSICS

The ultrafast structural deformation of NO2 in an intense laser field (1.0 PW/cm(2)) is studied by mass-resolved momentum imaging (MRMI) of the Op+ and Nq+ (p,q=1-3) fragment ions produced from NO2z+ through the Coulomb explosion processes, NO2z+--> Op++Nq++Or+ (z=p+q+r). The N-O distance just before the Coulomb explosion is elongated significantly from that in the electronic ground state, and it monotonically increases from 1.7 to 2.1 Angstrom as z increases from 4 to 9. The angle O-N-O bond angle increases toward a linear configuration as a function of z, which is interpreted in terms of the formation of the light-dressed potential energy surfaces. The two-body fragmentation pathways to produce NO+ and NO2+ are also investigated by the MRMI measurements to derive the extent of the asymmetrical bond elongation of one of the two N-O bonds. (C) 1999 American Institute of Physics. [S0021-9606(99)00443-2].

DOI： 10.1063/1.480233

Ultrafast deformation of the geometrical structure of CO2 induced in intense laser fields 査読有り

A Hishikawa, A Iwamae, K Yamanouchi

PHYSICAL REVIEW LETTERS 83 巻 ( 6 ) 頁： 1127 - 1130 1999年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMERICAN PHYSICAL SOC

Ultrafast deformation of geometrical structure of CO2 in an intense laser field (1.1 PW/cm(2) = 1.1 X 10(15) W/cm(2)) was investigated by momentum imaging of the fragment Op+ and Cq+ (p, q = 1-3) ions produced from CO2z+ through the Coulonnb explosion processes, CO2z+ --> Op+ + Cq+ + Or+ (z = p + q + r). The observed large mean amplitude along the angle O-C-O bond angle (similar to 40 degrees) was attributed to the ultrafast bending motion induced on the light-dressed potential energy surfaces.

DOI： 10.1103/PhysRevLett.83.1127

Vibrational propensity in the predissociation rate of SO2((C)over-tilde(1)B(2)) by two types of nodal patterns in vibrational wavefunctions 査読有り

T Sako, A Hishikawa, K Yamanouchi

CHEMICAL PHYSICS LETTERS 294 巻 ( 6 ) 頁： 571 - 578 1998年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

The absorption and laser-induced fluorescence spectra of the (C)over-tilde(1)B(2)-(X)over-tilde(1)A(1), band of SO2 were simultaneously measured between 221.5 and 208 nm under jet-cooled conditions. The fluorescence quantum yields above the dissociation threshold showed irregularity, reflecting a level specificity in the predissociation rate. The vibronic-level dependence in the predissociation rate was interpreted in terms of the nodal structure of the vibrational wavefunctions, constructed from a least-squares analysis of the observed vibrational energies in the C state. The vibrational wavefunctions can be categorized into two types of localized wavefunctions: one stretching along the dissociation coordinate which tends to afford a much faster dissociation rate than the other which folds perpendicularly to the dissociation coordinate. (C) 1998 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/s0009-2614(98)00922-1

Coulomb explosion dynamics of N-2 in intense laser field by mass-resolved momentum imaging 査読有り

A Hishikawa, A Iwamae, K Hoshina, M Kono, K Yamanouchi

CHEMICAL PHYSICS 231 巻 ( 2-3 ) 頁： 315 - 329 1998年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

The Coulomb explosion reactions of N-2, N-2((p+q)+) --> Np+ + Nq+ caused by the irradiation of intense laser light (0.73-6.9 PW/cm(2)) were investigated by high-resolution time-of-flight (TOF) mass spectroscopy and by the mass-resolved two-dimensional momentum imaging (MRMI) method. Six explosion pathways(p, q) = (1, 1), (1,2), (1,3), (2, 2), (2, 3) and (3, 3) in addition to (0, 1), (0,2) dissociation pathways were identified, whose assignments were securely performed both from the momentum matching between the fragment pair and their correlation with the laser-field intensity dependence. The MRMI method, which visualizes the radial and angular momentum distributions of mass-selected fragment ions on a two-dimensional momentum plane, was used to correlate ion fragments produced after the Coulomb explosion. By examining theoretically synthesized MRMI maps, it was found that the momentum distributions of the fragment ions in a wide momentum range can be extracted by the MRMI technique. The relative yields of the explosion pathways at six different laser-field intensities were evaluated from the three-dimensional integration of the MRMI maps, and the intensity dependence of the formation of singly and multiply charged parent N-2((p+q) +) ions prior to the fragmentation was derived. (C) 1998 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0301-0104(98)00025-1

Omega-type doubling reversal in the B-3 Pi(1) state of (HgAr)-Hg-200 as a probe of the long-range potential of the A(3)Pi(0)+ state 査読有り

A Hishikawa, H Sato, K Yamanouchi

JOURNAL OF CHEMICAL PHYSICS 108 巻 ( 22 ) 頁： 9202 - 9205 1998年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER INST PHYSICS

The mass-resolved excitation spectrum of the B (II1)-I-3-X(1)Sigma(+) transition of HgAr was measured by the two-color resonantly enhanced two-photon ionization method using a high-resolution reflectron time-of-flight mass spectrometer. The rotational structures were recorded with high spectral resolution (similar to 0.05 cm(-1))for the (upsilon(B),0) bands (upsilon(B) = 0 - 9) of a single isotopomer (HgAr)-Hg-200. From the rotational analysis, the presence of an Omega-type doubling was identified for the first time, which is caused by the rotational perturbation from the nearby highly excited vibrational levels of the A (II0+)-I-3 state. The spacing between the Omega-type doublers was found to exhibit a characteristic reversal as a function of upsilon(B). From the deperturbation of the Omega-type doubling, the vibrational level energies of the A state in the vibrationally highly excited region were derived, from which its long-range interaction potential was determined. (C) 1998 American Institute of Physics. [S0021-9606(98)02822-0].

DOI： 10.1063/1.476415

Mass-resolved VUV laser spectroscopy of XeAr: Two competing predissociation pathways in the C1 state 査読有り

SL Liu, A Hishikawa, K Yamanouchi

JOURNAL OF CHEMICAL PHYSICS 108 巻 ( 13 ) 頁： 5330 - 5337 1998年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER INST PHYSICS

Mass-resolved excitation spectra of the C1-X0(+) band of XeAr were measured under jet-cooled conditions using a tunable coherent vacuum ultraviolet (VUV) light (lambda similar to 130 nm) as an excitation light source and a high-resolution (m/Delta m similar to 1100) reflectron time-of-flight mass spectrometer. The rotational structure of the C1-X0(+) (upsilon',0) (upsilon'=2-6) vibronic bands were recorded by monitoring the parent (XeAr+)-Xe-132-Ar-40 ions and the fragment Xe-132(+) ions. From the analysis of the rotational structures, the existence of the two dissociation pathways from the C1 state was identified for the first time; i.e., (i) the rotationally dependent predissociation caused by an electron-rotation interaction (L- and/or S-uncoupling) with the dissociative state with 0(-) symmetry correlating with the Xe 6s'(1/2)(0) level, and (ii) the rotationally independent predissociation caused by the electrostatic interaction with a repulsive state with Omega = 1 symmetry correlated either with the Xe 6s(3/2)(1) level or the Xe 6s(3/2)(2) level. From the least-squares fit to the partially resolved rotational structures, the dissociation rates for these two pathways as well as the band origins and the rotational constants, were derived for the upsilon'=2-6 levels in the C1 state. (C) 1998 American Institute of Physics. [S0021-9606(98)01513-X].

DOI： 10.1063/1.475968

Rotational predissociation dynamics of H2O ((C)over-tilde(1)B(1)) by VUV laser-induced photofragment fluorescence spectroscopy 査読有り

SL Liu, A Hishikawa, K Yamanouchi

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 71 巻 ( 2 ) 頁： 355 - 362 1998年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：CHEMICAL SOC JAPAN

The rotational predissociation of water molecules in the vibrationless level of the (C) over tilde B-1(1) state was investigated under jet-cooled conditions (27-154 K) by exciting them with a tunable VUV laser in the wavelength range of 124.3-123.7 nm and by detecting the total fluorescence from electronically excited photofragments OH(A(2)Sigma (+)). Due to the simple one-photon selection rule and the efficient rotational cooling, individual low-J rotational transitions of the (C) over tilde B-1(1)-(X) over tilde (1)A(1) origin band were observed with almost no overlap in the laser-induced photofragment fluorescence (LIPF) spectrum. The widths and intensities of these rotational transitions exhibited pronounced dependence on the parent rotational levels in the (C) over tilde B-1(1) state. The least-squares analysis of the observed line-widths (FWHM) of the resolved rotational transitions, Gamma 's, showed that they are well described by the formula, Gamma = Gamma (0) + a(a)[J(a)'(2)], with optimized parameters Gamma (0) = 2.5(1) cm(-1) and a(a) = 0.63(1) cm(-1), indicating that (i) the homogeneous interaction couples the (C) over tilde B-1(1) state with the (A) over tilde B-1(1) state to form OH fragments in the electronically ground (2)Pi (i) state and (ii) the heterogeneous (a-axis orbital-rotation) interaction couples the (C) over tilde B-1(1) state with the (B) over tilde (1)A(1) state to form OH fragments in the electronically excited A(2)Sigma (+) state. By taking account of the rotational line-broadening effect, the least-squares analysis was also performed to fit the observed spectral intensities to derive the branching ratio of the OH(A(2)Sigma (+)) formation via the (B) over tilde (1)A(1) state of H2O. It was found that the OH(A(2)Sigma (+)) formation branching ratio can be expressed by an exponential form, exp(-gamma [J(a)'(2)]), which was proposed first by Hodgson et al. [Mol. Phys., 54, 351 (1985)], and reproduces well the observed rotational intensity pattern when gamma = 0.097(7). By using this branching ratio and the previous data for the absorption oscillator strength, the absolute cross section to yield OH(A(2)Sigma (+)) photofragments was obtained as a function of the excitation energy.

DOI： 10.1246/bcsj.71.355

Cross section for disalignment of excited neon atoms due to neon or helium atom collisions 査読有り

T Wakabayashi, A Yamamoto, T Yaneda, T Furutani, A Hishikawa, T Fujimoto

JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS 31 巻 ( 2 ) 頁： 341 - 359 1998年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IOP PUBLISHING LTD

In a positive column plasma of glow discharge in neon the population of metastable atoms (2p(5)3s configuration) is substantial. Linearly polarized pulsed laser light excited these atoms to one of the 2p(5)3p configuration levels, and the direct fluorescence was observed with its polarized components resolved. From the temporal development of the intensities of these components, the disalignment (depolarization) rate due to atom (neon or helium) collisions was determined. From its atom-density (<3 x 10(23) m(-3)) dependence the rate coefficient was determined, and from the temperature (42-650 K) dependence of the rate coefficient, the disalignment collision cross section was estimated as a function of energy in the energy range of the order of 10 meV. The cross section of the 2p(2) (Paschen notation) atoms has positive dependence on energy, while that of the 2p(7) atoms has a negative dependence. The cross sections thus determined serve asa quantitative test of the molecular potentials to the order of 1 cm(-1).
In order to confirm that the temperature of the metastable atoms in the plasma is equal to the temperature of the surrounding wall, an additional experiment was performed; the line profile of the CW laser-induced fluorescence was observed for a plasma at liquid nitrogen temperature, and the metastable atom temperature was found to be 78 K.

DOI： 10.1088/0953-4075/31/2/015

Mass-resolved two-dimensional momentum imaging of the Coulomb explosion of N-2 and SO2 in an intense laser field 査読有り

A Hishikawa, A Iwamae, K Hoshina, M Kono, K Yamanouchi

CHEMICAL PHYSICS LETTERS 282 巻 ( 3-4 ) 頁： 283 - 291 1998年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

The Coulomb explosion reactions of N-2 and SO2 caused by the irradiation of intense laser light were investigated by high-resolution mass spectroscopy. For N-2, from the least-squares fit to the split mass patterns for the N+, N2+ and N3+ channels, kinetic energy releases of six explosion pathways were determined. By rotating the laser polarization direction with respect to the detection axis, angular distributions for the singly and multiply charged atomic ion fragments were obtained and were converted to mass-resolved two-dimensional momentum imaging (MRMI) maps. This MRMI method was found to be useful to correlate ion fragments produced after the Coulomb explosion. MRMI was also applied to the Coulomb explosion of SO2. (C) 1998 Elsevier Science B.V.

DOI： 10.1016/S0009-2614(97)01325-0

Coulomb explosion dynamics of N2O in intense laser-field: Identification of new two-body and three-body fragmentation pathways 査読有り

A Hishikawa, A Iwamae, K Hoshina, M Kono, K Yamanouchi

RESEARCH ON CHEMICAL INTERMEDIATES 24 巻 ( 7 ) 頁： 765 - 784 1998年

記述言語：英語出版者・発行元：VSP BV

The Coulomb explosion process of N2O in an intense laser-field (similar to 5 PW/cm(2)) has been investigated by the high-resolution time-of-flight (TOF) spectroscopy. Six two-body explosion pathways involving the NO+, NO2+, N-2(+) molecular ions have been securely identified from the momentum-scaled TOF spectra of the fragment ions. Assuming a linear geometry, three-body explosion pathways were investigated by sequential and concerted explosion models, When the concerted model is adopted, the observed momentum distributions of six atomic ion channels; N+, N2+, N3+, O+, O2+ and O3+, were well fitted using the Gaussian momentum distribution with the optimized bond elongation factor of 2.2(3). From the yields of individual Coulomb explosion pathways determined by the fit, the abundance of the parent ions, N2Oz+ (z = 2-8), prior to the two- body and three-body explosion processes was found to have a smooth distribution with a maximum at z similar to 3.

DOI： 10.1163/156856798x00401

Experimental and theoretical exploration of photodissociation of SO2 via the (C)over-tilde(1)B(2) state: identification of the dissociation pathway 査読有り

H Katagiri, T Sako, A Hishikawa, T Yazaki, K Onda, K Yamanouchi, K Yoshino

JOURNAL OF MOLECULAR STRUCTURE 413 巻頁： 589 - 614 1997年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

The photodissociation reaction of SO2 via the (C) over tilde(1)B(2) state, SO2 ((C) over tilde(1)B(2)) --> SO((3) Sigma(-)) + O(P-3) was investigated by experimental and theoretical approaches cooperatively to clarify its dissociation mechanism. We measured the laser induced fluorescence (LIF) spectrum of the (C) over tilde-(X) over tilde band in the short UV wavelength region (210-200 nm) under jet-cooled conditions. The fluorescence quantum yields and the dissociation rates of individual vibronic levels were determined in the 220-200-nm region using (i) the LIF spectrum measured in the present study, (ii) that measured previously by Yamanouchi et al. (J. Mol. Struct, 352/353 (1995) 541) in the longer wavelength region above 210 nm, and (iii) the high-resolution absorption spectrum measured by Freeman et al. (Planet. Space. Sci. 32 (1984) 1125). The dissociation rates were also derived in the 210-200-nm region from the broadening of the rotational lines of the (C) over tilde-(X) over tilde vibronic transitions. It was found that the dissociation rates determined through two different procedures were consistent with each other, and that the rate increases almost exponentially as an excess energy above the dissociation threshold increases though there is a certain fluctuation of the dissociation rates reflecting a mode specificity. We also performed theoretical ab initio calculations to derive potential energy surfaces (PESs) of the electronic ground states and low-lying electronically excited states of SO2 within the MCSCF and MRCI levels. The theoretical calculations showed that (i) the PES of the 2(1)A' state (the (C) over tilde(1)B(2) state in C-2r symmetry), correlating with the SO((1) Delta) + O(D-1) asymptote, crosses with the repulsive singlet (3(1)A') state, correlating with the SO((3) Sigma(-)) + O(P-3) asymptote, to form a pseudo-seam, (ii) the crossing pseudo-seam of these two PESs is located near the equilibrium bent angles for the X and C states along the energy contour of similar to 9700 cm(-1) measured from the SO((3) Sigma(-)) + O(P-3) dissociation limit, and (iii) the crossing seam between the 2(1)A' ((C) over tilde(1)B(2)) and repulsive 2(3)A' states is located in a lower energy region than the singlet seam; at similar to 6700 cm(-1) measured from the SO((3) Sigma(-)) + O(P-3) dissociation limit. On the basis of the above experimental and theoretical results together with the previous experimental evidence, we propose that (i) the photodissociation reaction via the (C) over tilde state proceeds mainly through the vibronic mixing between the (C) over tilde state vibronic levels with the quasi-bound dissociation continuum of the electronic ground X(1)A(1) state, and (ii) the additional dissociation channels may be open through the crossing seam with the repulsive singlet (3(1)A') state and that with the repulsive tiplet (2(3)A') slate in their narrow crossing energy regions. (C) 1997 Elsevier Science B.V.

DOI： 10.1016/S0022-2860(97)00199-3

PHOFEX spectroscopy of HgNe and HgAr: Determination of the dissociation energies of the X-1 Sigma(+), A(3)II(0)+, and (BII1)-I-3 states 査読有り

T Tasaka, K Onda, A Hishikawa, K Yamanouchi

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 70 巻 ( 5 ) 頁： 1039 - 1045 1997年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：CHEMICAL SOC JAPAN

Photofragment excitation (PHOFEX) spectroscopy was applied to determine the dissociation energies of the B-3 Pi(1) states of HgAr and HgNe. The PHOFEX spectra were measured in the wavelength region where the laser-induced fluorescence spectrum of the B-3 Pi(1)-X-1 Sigma(+) transition exhibits a continuum structure by probing the photolysis product of Hg(6(3)P(1)) through the Hg(8(3)S(1)-6(3)P(1)) transition. By the spectral simulation of the threshold behavior of the high-resolution (Delta v approximate to 0.08 cm(-1)) PHOFEX spectrum, the thresholds for the photodissociation reaction, HgRg --> Hg(6(3)P(1)) + Rg, were determined to be 39447.9(3) and 39536.0(5) cm(-1) for Rg = Ne and Ar, respectively. From these thresholds, the dissociation energies, D-0's, of the B-3 Pi(1) states of HgNe and HgAr were determined to be D-0(B-3 Pi(1); HgNe)= 9.8(3) and Do(B-3 pi(1); HgAr)= 61.8(5) cm(-1), respectively. This direct determination of the dissociation energies of the B-3 Pi(1) states led to a determination of the D-0's for the X-1 Sigma(+) and A(3) Pi(0+) states; D-0(X-1 Sigma(+); HgNe)= 35.6(3), D-0(X-1 Sigma(+); HgAr)= 123.7(5), D-0(A(3) Pi(0+); HgNe)= 68.7(3), and D-0(A(3) Pi(0+); HgAr)= 348.8(6) cm(-1) In addition, the (v',0) vibronic bands of the B-3 Pi(1)-X-1 Sigma(+) transition of HgAr were re-measured with high resolution for v' = 0-8. From the transition wavenumbers of these vibronic bands, the Morse potential parameters were determined with high precision as omega(e) = 11.94(3) cm(-1) and omega(e)x(e) = 0.594(3) cm(-1).

DOI： 10.1246/bcsj.70.1039

Radiative lifetime measurements of the B (2)Sigma(+) state of BaH by laser spectroscopy 査読有り

LE Berg, K Ekvall, A Hishikawa, S Kelly

PHYSICA SCRIPTA 55 巻 ( 3 ) 頁： 269 - 272 1997年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ROYAL SWEDISH ACAD SCIENCES

By applying laser resonance methods in the near infrared wavelength region around 900 nm, a time-resolved experiment has been performed on the low lying B (2) Sigma(+) state of barium hydride. The radiative lifetime is shown to vary with the rotational quantum number due to perturbations between the low lying A' 2 Delta, A (2) Pi and B (2) Sigma(+) states. The following lifetime was obtained for the BaH molecule, where local perturbations are assumed to be negligible:
tau(B (2) Sigma(+)(upsilon' = 0, J = 5.5))= 125 +/- 2ns.

DOI： 10.1088/0031-8949/55/3/003

Femtosecond transition-state dynamics of dissociating OCS on the excited (1)Sigma(+) potential energy surface 査読有り

A Hishikawa, K Ohde, R Itakura, SL Liu, K Yamanouchi, K Yamashita

JOURNAL OF PHYSICAL CHEMISTRY A 101 巻 ( 4 ) 頁： 694 - 704 1997年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

Ultrafast photodissociation dynamics of OCS on the dissociative potential energy surface (PES) of the electronically excited (1) Sigma(+) state was investigated by photofragment excitation (PHOFEX) spectroscopy and time-dependent wavepacket calculations. The high-resolution PHOFEX spectrum of the entire (1) Sigma(+)-(1) Sigma(+) transition (63 300-69 350 cm(-1)) in the vacuum ultraviolet (vacuum UV) region was measured under jet-cooled conditions by using a tunable vacuum UV laser as an excitation light source and by monitoring the fragment S(S-1) atom. Due to sufficient vibrational and rotational cooling in a supersonic jet, a simple and distinct vibrational progression of the (1) Sigma(+)-(1) Sigma(+) band was recorded free from vibrational hot bands and the broadening by rotational structure. The autocorrelation function obtained from a Fourier transform of the PHOFEX spectra clearly exhibited recurrences with a period of 42 fs, corresponding to a period of the vibrational motion at the transition state along the direction perpendicular to the dissociation coordinate, This interpretation of the ultrafast motion in the transition-state region was supported by the wavepacket calculation on the ab initio PES obtained in the present study, which afforded a period of 48 fs for vibrational motion along the in-phase CO and CS stretching mode at the transition state on the ab initio PES. The distinct six peaks broadened due to the fast dissociation process were assigned to the transitions at the upsilon(TS) 0-5 levels, where upsilon(TS) represents a vibrational quantum number for the Feshbach resonances in the in-phase stretching mode at the transition state. For the upsilon(TS) = 0 peak, the narrowest width corresponding to the lifetime, tau(upsilon(TS)), of tau(0) = 133 fs was obtained. It was found that the dissociation lifetime first becomes shorter for a larger upsilon(TS), i.e., tau(1) = 44 fs and tau(2) = 27 fs, and then, the peak width becomes narrower for the higher vibrational states above upsilon(TS) = 2, with corresponding lifetimes of tau(3) = 47 fs and tau(4) = 44 fs. This deceleration of the dissociation rate for the larger upsilon(TS) states was interpreted as a result of trapping of a wave function in the in-phase stretching or the CO stretching vibrational motion suppressing the motion along the dissociation coordinate. All six main peaks in the PHOFEX spectra exhibited a characteristic asymmetric profile, originating from the interference between the zero-order discrete states for the in-phase stretching vibration at the transition state and the zero-order continuum states corresponding with the motion along the dissociation coordinate. In the main progression of the PHOFEX spectra, the reversal of the asymmetry direction was also observed. This q-reversal phenomenon was ascribed to the characteristic shape of the excited (1) Sigma(+) PES near the transition region which causes a phase shift in the wave functions in a narrow energy range.

DOI： 10.1021/jp962423m

Photodissociating small polyatomic molecules in the VUV region: Resonances in the (1)Sigma(+)-(1)Sigma(+) band of OCS 査読有り

K Yamanouchi, K Ohde, A Hishikawa, DM Neumark

CHEMICAL REACTIONS AND THEIR CONTROL ON THE FEMTOSECOND TIME SCALE XXTH SOLVAY CONFERENCE ON CHEMISTRY 101 巻頁： 789 - 797 1997年

Radiative lifetime measurements of the B2∑+ state of BaH by laser spectroscopy 査読有り

L. E. Berg, K. Ekvall, A. Hishikawa, S. Kelly

Physica Scripta 55 巻 ( 3 ) 頁： 269 - 272 1997年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Royal Swedish Academy of Sciences

By applying laser resonance methods in the near infrared wavelength region around 900 nm, a time-resolved experiment has been performed on the low lying B 2∑+ state of barium hydride. The radiative lifetime is shown to vary with the rotational quantum number due to perturbations between the low lying A′ 2Δ, A 2∏ and B 2∑+ states. The following lifetime was obtained for the BaH molecule, where local perturbations are assumed to be negligible: τ(B 2∑+(ν′ = 0, J = 5.5)) = 125 ± 2 ns.

DOI： 10.1088/0031-8949/55/3/003

Laser spectroscopy of SrH. Time-resolved measurements of the A(2)Pi state 査読有り

LE Berg, K Ekvall, A Hishikawa, S Kelly, C McGuinness

CHEMICAL PHYSICS LETTERS 255 巻 ( 4-6 ) 頁： 419 - 424 1996年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

In the near-infrared and red wavelength region around 680-760 nm, the spectrum of the A(2) Pi-X(2) Sigma transition of gaseous SrH appears. By applying laser spectroscopic methods, a time-resolved experiment has been performed on the low-lying A(2) Pi state of strontium hydride. No local influences on the A(2) Pi state were found due to interactions with the low-lying A'(2) Delta state, as in the case of the BaH molecule. The following zero-pressure lifetime was obtained for the SrH molecule: tau(A(2) Pi(1/2) (upsilon'=0))=33.8+/-1.9 ns.

DOI： 10.1016/0009-2614(96)00376-4

VUV photofragment excitation spectroscopy: Dynamics on dissociative potential surface of OCS 査読有り

K Ohde, A Hishikawa, K Yamanouchi

JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA 79 巻頁： 433 - 436 1996年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

The measurements of the photofragment excitation (PHOFEX) spectrum of jet-cooled OCS were extended toward the 152.6 and 150.6 nm peaks in the (1) Sigma(+)-(1) Sigma(+) transition. The PHOFEX spectra were recorded by scanning the wavelength of a tunable vacuum ultraviolet (VU) photolysis laser while probing the S(S-1) product by a second laser. Due to the efficient cooling of the sample in the free-jet expansion and the high-resolving power of the VUV laser, the homogeneous broadening of the dissociative state was derived directly from the observed PHOFEX spectrum. Based on the measured peak width, the lifetimes (tau) of the dissociative states at 152.6 and 150.6 nm were determined to be tau approximate to 50 and 31 fs. The PHOFEX peaks were found to exhibit an asymmetric line profile, and a fitting to a Fano line formula led to the asymmetry parameters, q= -8.1(2) and -13.0(6), for the 152.6 and 150.6 nm peaks, indicating a considerable mixing of the continuum and discrete states in that particular energy region. On the basis of the determined lifetimes and q values, together with the corresponding values for the 154.5 nm peak, tau approximate to 140 fs and q = -3.5(9), the dissociation dynamics on the repulsive (1) Sigma(+) surface was inferred.

DOI： 10.1016/0368-2048(96)02888-5

PHOTODISSOCIATION AND VIBRATIONAL DYNAMICS OF OCS IN THE VUV REGION 査読有り

K YAMANOUCHI, K OHDE, A HISHIKAWA, CD PIBEL

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 68 巻 ( 9 ) 頁： 2459 - 2464 1995年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：CHEMICAL SOC JAPAN

The photofragment excitation (PHOFEX) spectrum of jet-cooled OCS was remeasured for the 154.5 nm peak in the (1) Sigma(+)-(1) Sigma(+) transition by scanning a tunable vacuum ultraviolet (VUV) laser wavelength in the deep VUV region and by probing the S(S-1) product with a second laser. Due to the efficient cooling of the sample in the free-jet expansion and the high-resolving power of the VUV laser, the homogeneous broadening of the dissociative state was derived directly from the observed PHOFEX spectrum. Based on the measured peak width, the lifetime (tau) of the dissociative state was determined to be tau congruent to 0.14 ps. The profile of the PHOFEX peak was found to be asymmetric and was fit to a Fano line profile to derive the value of the asymmetry parameter, q=-3.5(9), which indicates a considerable mixing of the continuum and discrete states in that particular energy region. A Fourier-transform analysis was also performed for the whole distinct absorption feature in the 160-140 nm region measured by McCarthy and Vaida [J. Phys. Chem., 92, 5875 (1988)], and the period of the vibrational motion on the dissociative potential-energy surface was derived to be 41 fs. Using these pieces of experimental evidence, the dissociation dynamics on the repulsive (1) Sigma(+) surface in the 154.5 nm region was inferred.

DOI： 10.1246/bcsj.68.2459

MONTE-CARLO STUDY OF POPULATION AND ALIGNMENT RELAXATION BY TRAPPED LINE RADIATION 査読有り

A HISHIKAWA, T FUJIMOTO, P ERMAN

PHYSICAL REVIEW A 52 巻 ( 1 ) 頁： 189 - 196 1995年7月

ENERGY-DEPENDENT COLLISION CROSS-SECTION AS ESTIMATED FROM TEMPERATURE-DEPENDENT RATE COEFFICIENT - DISALIGNMENT OF EXCITED NEON ATOMS BY NEON COLLISIONS 査読有り

Y ISHITANI, H ISHIDA, T KITAGAWA, A HISHIKAWA, T FUJIMOTO

JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS 26 巻 ( 19 ) 頁： L671 - L675 1993年10月

記述言語：英語出版者・発行元：IOP PUBLISHING LTD

Laser-induced-fluorescence spectroscopy has been applied to a neon discharge plasma. A disalignment rate coefficient for 2p2 (Paschen notation; 2p5 3p configuration) atoms for neon atom collisions was determined at several atom temperatures (77-640 K). From the temperature dependence of the rate coefficient we estimate the cross section which explicitly depends on collision energy. It is found that the cross section has a positive energy dependence, which suggests that the OMEGA = 0 and 1 molecular potential curves correlating to the 2P2 State of neon are repulsive by about 100 cm-1 where these curves split by 10-20 cm-1.

DOI： 10.1088/0953-4075/26/19/007

LIFETIME MEASUREMENTS OF EXCITED MOLECULAR-STATES USING A TI-SAPPHIRE LASER - RADIATIVE LIFETIMES OF THE A(2)PI,B(2)SIGMA(+), AND C(2)PI STATES OF BACL 査読有り

LE BERG, A HISHIKAWA, A KARAWAJCZYK, T OLSSON

JOURNAL OF MOLECULAR SPECTROSCOPY 160 巻 ( 2 ) 頁： 593 - 595 1993年8月

LIFETIME MEASUREMENTS OF EXCITED MOLECULAR-STATES USING A TI SAPPHIRE LASER RADIATIVE LIFETIMES OF THE A(2)PI, B(2)SIGMA(+) AND C(2)PI STATES OF BAF 査読有り

LE BERG, T OLSSON, JC CHANTELOUP, A HISHIKAWA, P ROYEN

MOLECULAR PHYSICS 79 巻 ( 4 ) 頁： 721 - 725 1993年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：TAYLOR & FRANCIS LTD

A time resolved experiment on the lowest lying states of barium fluoride has been performed by applying laser resonance methods in the near infrared and green-blue wavelength regions. The A2PI and B2SIGMA+ states have been examined using Ti:sapphire laser excitations in the 710-850 nm wavelength region. The C2PI state was examined using the 496.5 nm Ar+ laser line and the lifetime of this state was in accordance with earlier measurements. The lifetimes obtained for the BaF molecule were: A2PI3/2, 46.1 +/- 0.9 ns; B2SIGMA+, 41.7 +/- 0.3 ns.

DOI： 10.1080/00268979300101571

LIFETIME MEASUREMENTS OF EXCITED MOLECULAR-STATES USING A TI-SAPPHIRE LASER - RADIATIVE LIFETIMES OF THE B(2)SIGMA+ STATE AND C(2)PI STATE OF BABR 査読有り

LE BERG, K EKVALL, E HEDIN, A HISHIKAWA, A KARAWAJCZYK, S KELLY, T OLSSON

CHEMICAL PHYSICS LETTERS 209 巻 ( 1-2 ) 頁： 47 - 51 1993年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

The barium bromide monohalide has been studied by using laser resonance methods in the near-infrared and green-blue wavelength regions. The low-lying B 2SIGMA+ state has been investigated in a time-resolved experiment using a Ti:sapphire laser operating around 900 nm. No influence on the radiative lifetime due to the B 2SIGMA interaction with the A'2DELTA-A 2PI complex was observed. The radiative lifetime of the C2PI state was examined using the 514.5 nm Ar+ laser line. The derived lifetime of this state was in agreement with earlier measurements. The following lifetimes were obtained for the BaBr molecule: B 2SIGMA+ 123.2 +/- 0.5 ns and C2PI(3/2)16.9+/-0.1 ns.

DOI： 10.1016/0009-2614(93)87199-d

PREDISSOCIATION EFFECTS IN THE A2-DELTA AND B2-SIGMA- STATES OF CD 査読有り

M DANIELSSON, P ERMAN, A HISHIKAWA, M LARSSON, E RACHLEWKALLNE, G SUNDSTROM

JOURNAL OF CHEMICAL PHYSICS 98 巻 ( 12 ) 頁： 9405 - 9411 1993年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER INST PHYSICS

Lifetimes have been measured for a large number of rotational levels of the A2DELTA and B2SIGMA-states in CD using the high frequency deflection technique. Four B-state levels are found to be influenced by predissociation by rotation which demands a lower value of the CD dissociation energy. The B state predissociations have also been studied using ab initio calculations. The A state levels above the dissociation limit are found to be weakly predissociated through interaction with the ground state continuum. The results are compared with earlier lifetime investigations of CH.

DOI： 10.1063/1.464372

THE ELECTRONIC-TRANSITION MOMENT AND THE OSCILLATOR STRENGTH OF THE SIH+ A1-PI-X1-SIGMA+ TRANSITION 査読有り

A HISHIKAWA, A KARAWAJCZYK

JOURNAL OF MOLECULAR SPECTROSCOPY 158 巻 ( 2 ) 頁： 479 - 481 1993年4月

EXPERIMENTAL-OBSERVATION OF DISALIGNMENT EFFECTS IN RADIATION TRAPPING PROCESSES 査読有り

P ERMAN, A HISHIKAWA

PHYSICA SCRIPTA 46 巻 ( 4 ) 頁： 348 - 353 1992年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ROYAL SWEDISH ACAD SCIENCES

Alignment effects at electron excitation measurements of atomic lifetimes have been studied at 20 keV energy using the High Frequency Deflection technique and a plastic polarizer. Disalignment associated with radiation trapping is observed directly for the first time. It has been pointed out that our previous results of the lifetime of the Ar 2p(i) levels might possibly have been influenced not only by radiation trapping itself but also by this "radiative disalignment". However, this influence has been found to be negligible thanks to small intrinsic alignment in almost all lines of noble gases investigated.

DOI： 10.1088/0031-8949/46/4/006

INFLUENCE OF RADIATION TRAPPING ON THE POLARIZATION DEGREE OF THE HE-I 501.6 NM LINE IN COLLISION SPECTROSCOPY 査読有り

A HISHIKAWA, H MIZUNO, M TANI, R OKASAKA

JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS 25 巻 ( 16 ) 頁： 3419 - 3431 1992年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IOP PUBLISHING LTD

The influence of radiation trapping on the polarization degree of the emission of the He I 501.6 nm line (3(1)P-2(1)S) is studied by experiments and a simulation. In the experiments, a particle (proton or electron) beam was injected into a helium gas cell. The accelerating energy was 100 keV for protons and 1.5, 2.5 and 5.0 keV for electrons. The polarization degree measured as a function of gas pressure showed a minimum at a certain gas pressure in accordance with results obtained by Hasselkamp et al. A Monte Carlo simulation method to treat the non-resonance line of the resonance state in a finite gas cell is presented. This simulation reproduces the minimum of the polarization degree as seen from experiments. We conclude that this minimum is caused by the asymmetry in the spatial distribution of atoms excited by collisions. We attempt to estimate a polarization degree not influenced by radiation trapping by fitting the simulated results to the experimental ones.

DOI： 10.1088/0953-4075/25/16/004

The g-u interference oscillations observed in the emission cross sections and the optical polarizations in he+—he collisions 査読有り

M. Tani, A. Hishikawa, R. Okasaka

Journal of Physics D: Applied Physics 24 巻 ( 6 ) 頁： 1359 - 1376 1991年3月

記述言語：英語掲載種別：研究論文（学術雑誌）

We have observed emission radiation from helium atoms excited in He+-He collisions by the direct and electron capture processes over the energy range 0.5-20 keV.The relative emission cross sections for transitions 21,3P-31,3S, 21,3S-31,3P and 21,3P-31,3Dhave been determined. Degrees of optical polarization have also been determined for theP- and D-state excitations. The emission cross section of the direct excitation and that ofthe electron capture excitation show oscillations against impact energy, which are inantiphase with each other. The polarization degrees for both processes are of nearly thesame magnitude and show weak oscillations in antiphase with each other. The oscillationsof the cross section and those of the polarization degree are in phase in some cases andin antiphase in other cases. These oscillations are interpreted as due to the interferencebetween the gerade and ungerade states of the helium quasimolecular ion. From theamplitude ratio and the phase correlation between the oscillations of the cross section andthose of the polarization degree we find that the predominant g-u interference pai r is nΠg-Πu. © IOP Publishing Ltd.

DOI： 10.1088/0953-4075/24/6/022

THE G-U INTERFERENCE OSCILLATIONS OBSERVED IN THE EMISSION CROSS-SECTIONS AND THE OPTICAL POLARIZATIONS IN HE+-HE COLLISIONS 査読有り

M TANI, A HISHIKAWA, R OKASAKA

JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS 24 巻 ( 6 ) 頁： 1359 - 1376 1991年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IOP PUBLISHING LTD

We have observed emission radiation from helium atoms excited in He+-He collisions by the direct and electron capture processes over the energy range 0.5-20 keV. The relative emission cross sections for transitions 2(1,3)P-3(1,3)S, 2(1,3)S-3(1,3)P and 2(1,3)P-3(1,3)D have been determined. Degrees of optical polarization have also been determined for the P- and D-state excitations. The emission cross section of the direct excitation and that of the electron capture excitation show oscillations against impact energy, which are in antiphase with each other. The polarization degrees for both processes are of nearly the same magnitude and show weak oscillations in antiphase with each other. The oscillations of the cross section and those of the polarization degree are in phase in some cases and in antiphase in other cases. These oscillations are interpreted as due to the interference between the gerade and ungerade states of the helium quasimolecular ion. From the amplitude ratio and the phase correlation between the oscillations of the cross section and those of the polarization degree we find that the predominant g-u interference pairs is PI-g-PI-u.

DOI： 10.1088/0953-4075/24/6/022

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