Faculty Profiles - HISHIKAWA, Akiyoshi

Imaging Ultrafast Dissociation Dynamics: OCS; Roaming in Formaldehyde International coauthorship

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

Springer Proceedings in Physics Vol. 300 page： 75 - 82 2024

Publisher：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 Reviewed International coauthorship

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

Physical Chemistry Chemical Physics Vol. 25 ( 37 ) page： 25408 - 25419 2023.9

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Royal Society of Chemistry (RSC)

Three-dimensional ion momentum imaging reveals that methane in two-color asymmetric intense laser fields has different waveform dependence for atomic and molecular hydrogen ion ejection.

DOI： 10.1039/d3cp02337k

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

Mizuho Fushitani, Makoto Yamada, Hikaru Fujise, Shigeki Owada, Tadashi Togashi, Kyo Nakajima, Makina Yabashi, Akitaka Matsuda, Yasumasa Hikosaka, Akiyoshi Hishikawa

Physical Review A Vol. 107 ( 2 ) page： L021101 2023.2

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：American Physical Society (APS)

DOI： 10.1103/PhysRevA.107.L021101

Orbital effects on tunnel-electron momentum distributions: Ar and H₂ studied by electron–ion coincidence momentum imaging Reviewed

Other Link： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevA.107.L021101/fulltext

Daimu Ikeya, Hikaru Fujise, Shinnosuke Inaba, Minami Takahashi, Masateru Yamamoto, Takeru Nakamura, Yu Nagao, Akitaka Matsuda, Mizuho Fushitani, Akiyoshi Hishikawa

Journal of Electron Spectroscopy and Related Phenomena Vol. 262 page： 147280 - 147280 2023.1

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 Vol. 12419 2023

Publisher：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

Asymmetric Dissociative Tunneling Ionization of Tetrafluoromethane in ω − 2ω Intense Laser Fields Invited Reviewed

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

Frontiers in Chemistry Vol. 10 2022.4

Authorship：Last author,　Corresponding author Publishing type：Research paper (scientific journal) Publisher：Frontiers Media {SA}

<jats:p>Dissociative ionization of tetrafluoromethane (CF<jats:sub>4</jats:sub>) in linearly polarized <jats:italic>ω</jats:italic>-2<jats:italic>ω</jats:italic> ultrashort intense laser fields (1.4 × 10<jats:sup>14</jats:sup> W/cm<jats:sup>2</jats:sup>, 800 and 400 nm) has been investigated by three-dimensional momentum ion imaging. The spatial distribution of <jats:inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m1"><mml:msubsup><mml:mrow><mml:mi mathvariant="normal">C</mml:mi><mml:mi mathvariant="normal">F</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msubsup></mml:math></jats:inline-formula> produced by CF<jats:sub>4</jats:sub> → <jats:inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m2"><mml:msubsup><mml:mrow><mml:mi mathvariant="normal">C</mml:mi><mml:mi mathvariant="normal">F</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msubsup></mml:math></jats:inline-formula> + F + e<jats:sup>−</jats:sup> exhibited a clear asymmetry with respect to the laser polarization direction. The degree of the asymmetry varies by the relative phase of the <jats:italic>ω</jats:italic> and 2<jats:italic>ω</jats:italic> 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 <jats:italic>ω</jats:italic>-2<jats:italic>ω</jats:italic> electric fields tends to be broken. Weak-field asymptotic theory (WFAT) shows that the tunneling ionization from the 4<jats:italic>t</jats:italic><jats:sub>2</jats:sub> second highest-occupied molecular orbital (HOMO-1) surpasses that from the 1<jats:italic>t</jats:italic><jats:sub>1</jats:sub> 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.</jats:p>

DOI： 10.3389/fchem.2022.857863

Helicity-dependent dissociative tunneling ionization of CF4 in multicycle circularly polarized intense laser fields Reviewed

H. Fujise, M. Uemura, H. Hasegawa, D. Ikeya, A. Matsuda, T. Morishita, L. B. Madsen, F. Jensen, O. I. Tolstikhin, A. Hishikawa

Physical Chemistry Chemical Physics Vol. 24 ( 15 ) page： 8962 - 8969 2022.4

Authorship：Last author,　Corresponding author Publishing type：Research paper (scientific journal) Publisher：Royal Society of Chemistry ({RSC})

Three-dimensional electron–ion coincidence momentum imaging reveals that the dissociative tunneling ionization of tetrafluoromethane (CF<sub>4</sub>) is sensitive to the helicity of the circularly polarized laser fields.

DOI： 10.1039/d1cp05858d

Post-Ionization Dynamics of the Polar Molecule OCS in Asymmetric Laser Fields Invited Reviewed International coauthorship

Tomoyuki Endo, Karl Michael Ziems, Martin Richter, Friedrich G. Fröbel, Akiyoshi Hishikawa, Stefanie Gräfe, Fran{\c{c } }ois L{\'{e } }gar{\'{e } }, Heide Ibrahim

Frontiers in Chemistry Vol. 10 2022.4

Language：English Publishing type：Research paper (scientific journal) Publisher：Frontiers Media {SA}

<jats:p>We have investigated the dissociation mechanisms of the prototypical heavy polar molecule OCS into the two break-up channels of the dication, OCS<jats:sup>2+</jats:sup> → O<jats:sup>+</jats:sup> + CS<jats:sup>+</jats:sup> and OC<jats:sup>+</jats:sup> + S<jats:sup>+</jats:sup>, 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 2<jats:italic>π</jats:italic>-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 2<jats:italic>π</jats:italic>-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.</jats:p>

DOI： 10.3389/fchem.2022.859750

Electronic relaxation and dissociation dynamics in formaldehyde: pump wavelength dependence Reviewed

Tomoyuki Endo, Simon P. Neville, Philippe Lassonde, Chen Qu, Hikaru Fujise, Mizuho Fushitani, Akiyoshi Hishikawa, Paul L. Houston, Joel M. Bowman, François Légaré, Michael S. Schuurman, Heide Ibrahim

Physical Chemistry Chemical Physics Vol. 24 ( 3 ) page： 1779 - 1786 2022.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Royal Society of Chemistry ({RSC})

The effect of the incident UV pump wavelength on the subsequent excited state dynamics, elec- tronic relaxation, and ultimate dissociation of formaldehyde is studied using ﬁrst principles simu- lation and...

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

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

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

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

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

Association Reaction of Gaseous C2H4 in Femtosecond Laser Filaments Studied by Time-of-Flight Mass Spectrometry Reviewed

Akitaka Matsuda, Kentaro Tani, Yukari Takeuchi, Yui Hayakawa, Akiyoshi Hishikawa

ACS Omega Vol. 6 ( 44 ) page： 29862 - 29868 2021.11

Time-resolved shot-by-shot photoelectron spectroscopy of autoionizing Xe+ states by EUV–free-electron-laser and near-IR laser pulses Reviewed

Akiyoshi Hishikawa

Physical Review A Vol. 104 ( 2 ) 2021.8

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：American Physical Society (APS)

DOI： 10.1103/PhysRevA.104.023102

Other Link： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevA.104.023102/fulltext

Time-resolved photoelectron imaging of complex resonances in molecular nitrogen Reviewed International coauthorship

Mizuho Fushitani, Stephen T. Pratt, Daehyun You, Shu Saito, Yu Luo, Kiyoshi Ueda, Hikaru Fujise, Akiyoshi Hishikawa, Heide Ibrahim, François Légaré, Per Johnsson, Jasper Peschel, Emma R. Simpson, Anna Olofsson, Johan Mauritsson, Paolo Antonio Carpeggiani, Praveen Kumar Maroju, Matteo Moioli, Dominik Ertel, Ronak Shah, Giuseppe Sansone, Tamás Csizmadia, Mathieu Dumergue, N. G. Harshitha, Sergei Kühn, Carlo Callegari, Oksana Plekan, Michele Di Fraia, Miltcho B. Danailov, Alexander Demidovich, Luca Giannessi, Lorenzo Raimondi, Marco Zangrando, Giovanni De Ninno, Primož Rebernik Ribič, Kevin C. Prince

The Journal of Chemical Physics Vol. 154 ( 14 ) page： 144305 - 144305 2021.4

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：AIP Publishing

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, N , 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. 2

DOI： 10.1063/5.0046577

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

Other Link： https://aip.scitation.org/doi/pdf/10.1063/5.0046577

Tomoyuki Endo, Simon P. Neville, Vincent Wanie, Samuel Beaulieu, Chen Qu, Philippe Lassonde, Bruno E. Schmidt, Hikaru Fujise, Mizuho Fushitani, Akiyoshi Hishikawa, Paul L. Houston, Joel M. Bowman, Michael S. Schuurman, François Légaré, Heide Ibrahim

AIP Conference Proceedings Vol. 2343 2021.3

Language：Japanese Publishing type：Research paper (international 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