研究者詳細 - 菱川　明栄

State-selective dissociative double ionization of CH3I and CH2I2 via I 4d core-hole states studied by multi-electron-ion coincidence spectroscopy 査読有り

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

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 via 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

Open Access

Dissociative ionization and Coulomb explosion of CH4 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 CF4 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