Papers - HISHIKAWA, Akiyoshi

Ultrafast two-photon Rabi oscillations in excited He driven by femtosecond intense laser fields Reviewed

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

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

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Language：Japanese   Publishing type：Research paper (international conference proceedings)   Publisher：IOP PUBLISHING LTD  

We demonstrate ultrafast multiphoton coherent excitation in near-infrared intense laser fields (<= 10 TW/cm(2)) using excited helium in the 1s2p (P-1) 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

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

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

PHYSICAL REVIEW A   Vol. 90 ( 5 ) page： 053403   2014.11

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

A multiphoton ionization process of He in intense extreme ultraviolet free-electron laser fields is investigated in a photon energy range of hv = 20.1-20.8 eV 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+(2s S-2) 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

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Photoelectron-photoion correlation in ultrafast multichannel photoionization of Ar Reviewed

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

JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS   Vol. 47 ( 19 ) page： 195602   2014.10

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

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

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Time-resolved laser Coulomb explosion imaging using few-cycle intense laser pulses: Application to exploding CS2 in highly charged states Reviewed

Akitaka Matsuda, Eiji J. Takahashi, Akiyoshi Hishikawa

JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA   Vol. 195   page： 327 - 331   2014.8

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER  

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, similar to 10(15) W/cm(2)) 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 C S bonds. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.elspec.2013.12.011

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Preface Reviewed

Hiroshi Daimon, Akiyoshi Hishikawa, Catalin Miron

JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA   Vol. 195   page： 285 - 286   2014.8

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Language：English   Publisher：ELSEVIER SCIENCE BV  

DOI： 10.1016/j.elspec.2014.07.013

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Special issue on ultrafast electron and molecular dynamics Preface Reviewed

Fernando Martin, Akiyoshi Hishikawa, Marc Vrakking

JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS   Vol. 47 ( 12 )   2014.6

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DOI： 10.1088/0953-4075/47/12/120201

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Dissociative ionization of NO in few-cycle intense laser fields : Effects of pi-sigma electronic transition Reviewed

Tomoyuki Endo, Mizuho Fushitani, Akitaka Matsuda, Akiyoshi Hishikawa

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

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IOP PUBLISHING LTD  

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 pi - sigma electronic transition is clearly reflected in the spatial anisotropy of the fragment ion, N+.

DOI： 10.1088/1742-6596/488/3/032025

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

Chien-Nan Liu, Akiyoshi Hishikawa, Toru Morishita

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

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Language：Japanese   Publishing type：Research paper (international conference proceedings)   Publisher：IOP PUBLISHING LTD  

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. We identify the mechanism of the enhanced three-photon absorption probability as observed in the experiment.

DOI： 10.1088/1742-6596/488/3/032047

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

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

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Other Link： http://orcid.org/0000-0003-1444-8917

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

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Language：Japanese   Publisher：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

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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

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Language：Japanese   Publisher：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

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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

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Language：Japanese   Publisher：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

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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

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Language：Japanese   Publisher：Optics InfoBase Conference Papers  

Intensity dependence of polarized He (21P) atoms in intense NIR laser fields are investigated by single-shot photoelectron spectroscopy, revealing two-photon Rabi oscillations between the initial 1s2p and 1snf (n = 5,6) Rydberg states. © 2014 OSA.

DOI： 10.1364/up.2014.08.tue.p2.4

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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

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Language：Japanese   Publisher：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

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

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

PHYSICAL REVIEW A   Vol. 88 ( 6 ) page： 063422   2013.12

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

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 sigma((2)) = 4.1(6) x 10(-52) cm(4) 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.

DOI： 10.1103/PhysRevA.88.063422

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Compact XFEL and AMO sciences: SACLA and SCSS Reviewed

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

JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS   Vol. 46 ( 16 ) page： 164001   2013.8

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

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.

DOI： 10.1088/0953-4075/46/16/164001

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

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   Vol. 88 ( 023421 ) page： 023421   2013.8

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DOI： DOI: 10.1103/PhysRevA.88.023421]

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

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

PHYSICAL REVIEW A   Vol. 88 ( 2 )   2013.8

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

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 Ar2+ ionization threshold.

DOI： 10.1103/PhysRevA.88.023421

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Time-resolved four-body coulomb explosion imaging of correlated dynamics of hydrogen atoms in acetylene dication Reviewed

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

EPJ Web of Conferences   Vol. 41   2013

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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

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Ultrafast nonlinear double excitations of he in intense EUV FEL fields Reviewed

M. Fushitani, Y. Hikosaka, A. Matsuda, C. N. Liu, T. Morishita, E. Shigemasa, A. Hishikawa

EPJ Web of Conferences   Vol. 41   2013

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Language：English   Publishing type：Research paper (international conference proceedings)  

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

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