Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Akagi, Hiroshi; Kasajima, Tatsuya*; Kumada, Takayuki; Itakura, Ryuji; Yokoyama, Atsushi; Hasegawa, Hirokazu*; Oshima, Yasuhiro*
Physical Review A, 91(6), p.063416_1 - 063416_7, 2015/06
Times Cited Count：7 Percentile：38.91(Optics)We propose a strategy of isotope-selective ionization for a binary mixture of isotopologues of homonuclear diatomic molecules, utilizing field-free alignment with a train of femtosecond laser pulses. Field-free alignment can be achieved simultaneously for two isotopologues consisting of two atoms with the same atomic mass number 
or 
, utilizing a pulse train with their time interval of T
= T() = T(), where T() and T() are the rotational revival times of the isotopologues. We demonstrate experimentally that a train of four alignment pulses with their interval of T ( = 14, = 15) creates transiently aligned 
N
and anti-aligned 
N just before T/2 after the last pulse, and vice versa just after T/2. Highly isotope-selective N ionization is achieved at these timings with another femtosecond laser pulse, which induces the non-resonant multiphoton ionization with the cross section remarkably depending on the angle between the molecular axis and the laser electric field direction. The ion yield ratio I(N
)/I(N) ranges from 0.49 to 2.00, which is wider than the range obtained with single alignment pulse.
Akagi, Hiroshi; Kasajima, Tatsuya; Kumada, Takayuki; Itakura, Ryuji; Yokoyama, Atsushi; Hasegawa, Hirokazu*; Oshima, Yasuhiro*
Applied Physics B, 109(1), p.75 - 80, 2012/10
Times Cited Count：16 Percentile：61.38(Optics)We demonstrate a laser nitrogen isotope separation, which is based on field-free alignment and angular dependent ionization of N and N isotopomers. A linearly-polarized short laser pulse (
795 nm, 
60 fs) creates rotational wave packets in the isotopomers, which periodically revive with different revival times as a result of different moments of inertia. Another linearly-polarized short laser pulse (795 nm, 60 fs) ionizes one of the isotopomers selectively as a result of their different angular distributions. In the present experiments, the ion yield ratio 
[= 
(N)/(N)] can be changed in the range from 0.85 to 1.22, depending on the time delay between the two laser pulses.
Matsuoka, Leo; Kasajima, Tatsuya; Hashimoto, Masashi; Yokoyama, Keiichi
Journal of the Korean Physical Society, 59(4), p.2897 - 2900, 2011/10
Times Cited Count：13 Percentile：62.2(Physics, Multidisciplinary)Matsuoka, Leo; Kasajima, Tatsuya; Hashimoto, Masashi; Yokoyama, Keiichi
arXiv.org (Internet), 5 Pages, 2011/04
Kasajima, Tatsuya; Yokoyama, Keiichi; Matsuoka, Leo; Yokoyama, Atsushi
Chemical Physics Letters, 485(1-3), p.45 - 48, 2010/01
Times Cited Count：1 Percentile：3.01(Chemistry, Physical)Yokoyama, Keiichi; Matsuoka, Leo; Kasajima, Tatsuya; Tsubouchi, Masaaki; Yokoyama, Atsushi
Proceedings of 5th Asian Symposium on Intense Laser Science (ASILS-5), p.113 - 119, 2009/05
The current status of the fundamental research for the quantum control conducted at Kansai Photon Science Institute are reported. In particular, the experimental studies on vibrational control of diatomic molecules, the nitrogen molecules and the iodine molecules, and the theoretical study on the rotational control of the diatomic molecule, the cesium iodide molecule (CsI), are introduced. For the study of vibrational control of N, the vibration selective excitation with extremely broadband white light pulses is demonstrated by tuning the time interval of a linearly chirped white light pulse pair. For the study of vibrational control of I, the direction control of stimulated impulsive Raman transition is demonstrated by changing the sign of the chirp rate. For the study of rotational control of CsI, the isotope-selective population distribution transfer is demonstrated numerically using frequency comb in the terahertz-wave region.
Kasajima, Tatsuya; Yokoyama, Keiichi; Matsuoka, Leo; Yokoyama, Atsushi
no journal, ,
no abstracts in English
in the B 
(0
) stateMatsuoka, Leo; Yokoyama, Keiichi; Kasajima, Tatsuya; Yokoyama, Atsushi
no journal, ,
no abstracts in English
Kasajima, Tatsuya; Tsubouchi, Masaaki; Matsuoka, Leo; Yokoyama, Keiichi; Yokoyama, Atsushi
no journal, ,
no abstracts in English
Yokoyama, Keiichi; Matsuoka, Leo; Akagi, Hiroshi; Kasajima, Tatsuya; Tsubouchi, Masaaki
no journal, ,
Pure rotational transition shows evenly spaced line spectra, the rotational comb, when the molecule is diatomic and has a closed-shell electronic structure. Let us consider irradiating an optical frequency comb tuned to the rotational comb. We studied numerically the dynamics of the molecular rotation in such a irradiation. As a result, the dynamics was found to obey the diffusion equation within the quantum mechanics. Also, we found that an isotope-selective excitation based on this scheme is a novel example of coherent control effective even at high temperature.
Kasajima, Tatsuya; Tsubouchi, Masaaki; Yokoyama, Keiichi
no journal, ,
no abstracts in English
Matsuoka, Leo; Kasajima, Tatsuya; Yokoyama, Keiichi
no journal, ,
no abstracts in English
Yokoyama, Keiichi; Kasajima, Tatsuya; Matsuoka, Leo; Hashimoto, Masashi; Tsubouchi, Masaaki; Sugiyama, Akira; Yokoyama, Atsushi
no journal, ,
Technological innovation in the isotope separation of long-lived fission products is demanded. Quantum control may provide a breakthrough in such technology. Recently, we proposed a novel scheme based on cascaded excitation of rotation in diatomic molecules. Both (1) demonstration of quantum walk by Raman transition using a conventional Ti:Sapphire laser and (2) development of high-power terahertz-wave source are concurrently proceeded. (1) Cascaded excitation of rotation in the nitrogen molecule N will be induced by impulsive Raman transitions. At present, we are developing a method to observe the incoherent population distribution among rotational states, which involves femotosecond coherent anti-Stokes Raman scattering. Also, current status of (2) development of high-power terahertz-wave source will be briefly introduced, including optical rectification in ZnTe and LiNbO
crystals and a plan for construction of a high-power, picosecond laser as a driver laser.
Yokoyama, Keiichi; Matsuoka, Leo; Kasajima, Tatsuya; Tsubouchi, Masaaki; Hashimoto, Masashi
no journal, ,
Recent progress in laser science enables us precise manipulation of molecules by taking advantages of the wave nature of matter. These techniques are called coherent quantum control. Using coherent quantum control, a breakthrough in laser isotope separation may be realized. Actually, we proposed a novel scheme of isotope selective excitation, which is based on cascaded excitation of rotation in diatomic molecules. A numerical simulation done by solving a coupled Schroedinger equation for the cesium iodide molecule has shown that the separation factor reaches three orders of magnitude higher than that by the conventional scheme. The current status of the experimental demonstration undergoing in our institute will be introduced.
Akagi, Hiroshi; Kasajima, Tatsuya; Kumada, Takayuki; Itakura, Ryuji; Yokoyama, Atsushi; Hasegawa, Hirokazu*; Oshima, Yasuhiro*
no journal, ,
no abstracts in English
Kasajima, Tatsuya; Tsubouchi, Masaaki; Matsuoka, Leo; Yokoyama, Keiichi
no journal, ,
no abstracts in English
Akagi, Hiroshi; Kasajima, Tatsuya; Kumada, Takayuki; Itakura, Ryuji; Yokoyama, Atsushi; Hasegawa, Hirokazu*; Oshima, Yasuhiro*
no journal, ,
We have experimentally realized a new laser isotope separation method, utilizing molecular laser alignment and angular dependent ionization. We have introduced gas mixture including N and N isotopomers into a vacuum chamber, and have shined a linearly-polarized laser pulse onto the gas jet to produce molecular alignment state of the isotopomers. We have shined another laser pulse to ionize the isotopomers through the nonresonant multiphoton ionization. Ion yield ratio N/N has varied from 0.85 to 1.22, depending on delay time between the two laser pulses.
Yokoyama, Keiichi; Hashimoto, Masashi; Matsuoka, Leo; Kasajima, Tatsuya
no journal, ,
Enhancement of isotope separation by a phase-locked pulse train of terahertz wave is numerically demonstrated by solving close-coupling time-dependent Schroedinger equations. The terahertz wave is transform-limited and has the center frequency of 0.5 THz with the bandwidth of 0.55 THz FWHM. Individual pulse energy is 1.56 
J. Irradiation of 16 such pulses to lithium chloride vapor is simulated at 70 K. At the pulse interval of 24.04 ps, the rotational state distribution of 
Li
Cl is largely displaced, while that of Li
Cl is not. Assuming multi-photon decomposition as a subsequent process, the enrichment factor is calculated and found to be enhanced by three orders of magnitude, while decomposition probability of the target isotope is kept up 0.3.
Kasajima, Tatsuya; Yokoyama, Keiichi
no journal, ,
no abstracts in English
Akagi, Hiroshi; Kasajima, Tatsuya; Kumada, Takayuki; Itakura, Ryuji; Yokoyama, Atsushi; Hasegawa, Hirokazu*; Oshima, Yasuhiro*
no journal, ,
We have proposed a laser isotope separation method utilizing molecular alignment and non-resonant multiphoton ionization, and demonstrated isotope-selective ionization of N and N isotopomers. In the present work, we use a train of four identical pulses to create rotational wave packets in the isotopomers. When we set the pulse interval to 125.7 ps, which corresponds to the fifteenth full revival of N and the fourteenth full revival of N, we obtained ca. two-times higher selectivity than that in the one-pulse alignment case.
