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Dive into the research topics where Akitaka Matsuda is active.

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Featured researches published by Akitaka Matsuda.


Journal of Chemical Physics | 2008

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

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

The isomerization of acetylene via hydrogen migration in intense laser fields (8 x 10(14) W/cm2) has been investigated by coincidence momentum imaging of the three-body Coulomb explosion process, C2H2 (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 ( approximately 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 ( approximately 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.


Physical Chemistry Chemical Physics | 2011

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

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

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 (∼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(+).


Journal of Physical Chemistry A | 2009

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

Akitaka Matsuda; Mizuho Fushitani; Richard D. Thomas; Vitali Zhaunerchyk; Akiyoshi Hishikawa

The fragmentation of deuterated benzene (C6D6) in ultrashort intense laser fields (9 fs, 1 x 10(15) W/cm2) is studied by the ion-coincidence momentum imaging technique. Five two-body and eight three-body Coulomb explosion pathways from the trication (C6D6(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.


Journal of Chemical Physics | 2007

Dalitz plot analysis of Coulomb exploding O3 in ultrashort intense laser fields

Akitaka Matsuda; Eiji J. Takahashi; Akiyoshi Hishikawa

The three-body Coulomb explosion of O3, O3(3+)-->O++O++O+, in ultrashort intense laser fields (2x10(15) W/cm2) 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 O3 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 O3.


Journal of Chemical Physics | 2006

Nanosecond rapid freezing of liquid benzene under shock compression studied by time-resolved coherent anti-Stokes Raman spectroscopy

Akitaka Matsuda; Ken-ichi Kondo; Kazutaka G. Nakamura

Nanosecond time-resolved coherent anti-Stokes Raman spectroscopy is used to investigate the shock-induced liquid-solid phase transition and crystallization of liquid benzene. Temporal evolution of the Raman shift of the ring-breathing and C-H stretching modes is investigated. A metastable supercompressed state and a liquid-solid phase transition are observed under shock compression. Time-resolved Raman spectra reveal that the liquid state is initially a metastable state and rapidly transforms to the solid state within 25 ns under shock compression at 4.2 GPa.


Review of Scientific Instruments | 2011

A magnetic-bottle multi-electron-ion coincidence spectrometer

Akitaka Matsuda; Mizuho Fushitani; Chien-Ming Tseng; Yasumasa Hikosaka; John H. D. Eland; Akiyoshi Hishikawa

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, CS(2) → CS(2)(2+) + e(-) + e(-), in ultrashort intense laser fields (2.8 × 10(13) W/cm(2), 280 fs, 1030 nm) to clarify the electron correlation below the rescattering threshold.


Japanese Journal of Applied Physics | 2005

Flyer Acceleration by Pulsed Laser and its Application to Shock-Recovery Experiment on MnF2

Teruhisa Hongo; Akitaka Matsuda; Ken-ichi Kondo; Kazutaka G. Nakamura; Toshiyuki Atou

An experimental method using a laser-driven flyer has been developed for a shock-recovery experiment. A laser-driven flyer has been accelerated to a high speed using a plasma-confinement target assembly with a relatively modest laser intensity (<5 GW/cm2) and its acceleration history has been monitored. A shock recovery experiment of rutile-type MnF2 is performed using the laser-driven flyer with a velocity of 1.1 km/s and a metastable phase (α-PbO2-type MnF2) is recovered with a yield of 83.2%.


Science and Technology of Advanced Materials | 2004

Materials dynamics under nanosecond pulsed pressure loading

Akitaka Matsuda; Teruhisa Hongo; Hirofumi Nagao; Kazutaka G. Nakamura; Ken-ichi Kondo

Abstract A nanosecond pressure pulse is generated by focusing a nanosecond-pulsed laser onto an aluminum target with plasma confined geometry. A spatially uniform pressure pulse is generated by focusing laser beams with a flat-top spatial energy distribution. High-pressure pulse loading and recovery experiments were performed on yttria-doped (3 mol%) tetragonal zirconia polycrystals at 11 GPa. In the pressure-loaded region, the monoclinic phase was uniformely formed. The transition ratio was approximately 30%. Nanosecond time-resolved Raman spectroscopy was performed on polytetrafluoroethylene under high-pressure pulse loading at 1 GPa, and rapid structural phase transition within 10 ns was revealed.


Japanese Journal of Applied Physics | 2004

Nanosecond Time-Resolved Stimulated Raman Spectra of Benzene under Shock Compression up to 4.2 GPa: Observation of Liquid-Solid Phase Transition

Akitaka Matsuda; Ken-ichi Kondo; Kazutaka G. Nakamura

Nanosecond time-resolved stimulated Raman spectroscopy is used to investigate the shock-induced phase transition of liquid benzene. A supercooled state and a liquid-solid phase transition are observed at shock pressures above 2.8 GPa. Time-resolved Raman spectra reveal that the liquid state is initially preserved and rapidly transforms to the solid state under shock compression at 4.2 GPa. Rapid nucleation and growth on a micrometer scale occurs within 20 ns.


Archive | 2012

Visualizing Correlated Dynamics of Hydrogen Atoms in Acetylene Dication by Time-Resolved Four-Body Coulomb Explosion Imaging

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

Ultrafast hydrogen migration in deuterated acetylene dication (C\({}_{2}{\mathrm{D}}_{2}^{2+}\)) is studied by time-resolved four-body Coulomb explosion imaging, C2D\({}_{2}^{4+}\, \rightarrow \,\,{\mathrm{D}}^{+} +{ \mathrm{C}}^{+} +{ \mathrm{C}}^{+} +{ \mathrm{D}}^{+}\), using a pair of few-cycle intense laser pulses (9 fs, 1. 3 ×1014 W/cm2). 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 non-planar geometries.

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Kazutaka G. Nakamura

Tokyo Institute of Technology

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Ken-ichi Kondo

Tokyo Institute of Technology

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