Bromine-isotope selective ionization using field-free alignment of IBr isotopologues with a switched nanosecond laser pulse

Akagi, Hiroshi*; Kumada, Takayuki; Otobe, Tomohito*; Itakura, Ryuji*; Hasegawa, Hirokazu*; Oshima, Yasuhiro*

Chemistry Letters, 49(4), p.416 - 418, 2020/04

https://doi.org/10.1246/cl.200024

Isotope-selective ionization utilizing field-free alignment of isotopologues with a train of femtosecond laser pulses

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

https://doi.org/10.1103/PhysRevA.91.063416

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.

Isotope-selective ionization utilizing molecular alignment and non-resonant multiphoton ionization

Akagi, Hiroshi; Kasajima, Tatsuya; Kumada, Takayuki; Itakura, Ryuji; Yokoyama, Atsushi; Hasegawa, Hirokazu*; Oshima, Yasuhiro*

Applied Physics B, 109(1), p.75 - 80, 2012/10

https://doi.org/10.1007/s00340-012-5222-3

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.

Coherent correlation between nonadiabatic rotational excitation and angle-dependent ionization of NO in intense laser fields

Itakura, Ryuji; Hasegawa, Hirokazu*; Kurosaki, Yuzuru; Yokoyama, Atsushi; Oshima, Yasuhiro*

Journal of Physical Chemistry A, 114(42), p.11202 - 11209, 2010/07

https://doi.org/10.1021/jp102840t

When neutral NO molecules are partly ionized in intense laser fields ( 35 TW/cm), a hole in the rotational wave packet of the remaining neutral NO is created by the ionization, whose rate depends on the alignment angle of the molecular axis with respect to the laser polarization direction. Rotational state distributions of NO are experimentally observed and then the characteristic feature that the population at higher levels is increased by the ionization can be identified. Numerical calculation for solving time-dependent rotational Schrodinger equations including the effect of the ionization is carried out. The numerical results suggest that NO molecules aligned perpendicular to the laser polarization direction are dominantly ionized at the peak intensity of = 42 TW/cm, where the multiphoton ionization is preferred rather than the tunneling ionization.

Ion-irradiation effects of hydrogen absorption in palladium metal

Yoneda, Yasuhiro; Tamura, Kazuhisa; Abe, Hiroshi; Oshima, Takeshi; Morimoto, Ryo*; Uchida, Hirohisa*; Mizuki, Junichiro

Transactions of the Materials Research Society of Japan, 33(4), p.1053 - 1056, 2008/12

The effect of ion irradiation on palladium (Pd) metal was investigated by hydrogen-absorption measurements, SEM microscopy and synchrotron X-ray diffraction. N irradiation was made with an acceleration energy 350 keV. The initial hydrogen absorption rate of the irradiated Pd was three times larger than that of non-irradiated Pd. The microscopic structure was investigated by using the pair-distribution function (PDF) obtained by X-ray diffraction. Although the average structure of the Pd was f.c.c, the Pd atoms displaced and two occupancy sites are revealed. This site occupancy is closely related with the hydrogen-absorption rate.

Local modification of hardness in FeCu alloys by using swift heavy ion irradiation

Nakagawa, Sho*; Hori, Fuminobu*; Chimi, Yasuhiro; Ishikawa, Norito; Kitagawa, Michiharu*; Oshima, Ryuichiro*; Tobita, Toru; Taniguchi, Ryoichi*; Suzuki, Masahide; Iwase, Akihiro*

Nuclear Instruments and Methods in Physics Research B, 257(1-2), p.397 - 401, 2007/04

https://doi.org/10.1016/j.nimb.2007.01.263

Supersaturated Fe-1.2wt.%Cu alloys were irradiated with 200-MeV Xe and 200-MeV Au ions at elevated temperatures. To make an irradiated region and an unirradiated region in a specimen, a masking plate was put on the specimen during the irradiation. After the irradiation, the hardness was measured by using a conventional microhardness tester or a nano-indenter. We have found that the hardness only in irradiated region increases by the irradiation. The boundary of irradiated and unirradiated regions can be clearly identified by the difference in hardness. The present result implies that swift heavy ion irradiation can be used for the local modification of hardness in supersaturated alloys.

Effect of ro-vibrational coupling on rotational wavepacket of N

Yokoyama, Atsushi; Akagi, Hiroshi; Kumada, Takayuki; Itakura, Ryuji; Hasegawa, Hirokazu*; Oshima, Yasuhiro*

no journal, , 

Recently, we demonstrated a nitrogen isotope separation based on isotopically different time-evolution of rotational wavepacket by using N/N mixture, in which at first rotational wavepackets of isotopomers were created by the irradiation of a femtosecond laser pulse, then a specific isotopomer molecules were ionized by another femtosecond laser pulse at the time when they align. In the experiment, we found peak shapes of the N intensity were distorted as the evolution time passes. The behavior was not predicted by a rigid rotor model. In this work, we examined the effect of ro-vibrational coupling on this behavior by solving a time-dependent Schrdinger equation including the coupling. As a result, we elucidated that the simulation agreed well with the experimental results and that the effect of ro-vibrational coupling became larger as the rotational temperature increased.

Isotope-selective rotational excitation with a sequence of femto-second laser pulses

Akagi, Hiroshi; Kasajima, Tatsuya*; Kumada, Takayuki; Itakura, Ryuji; Yokoyama, Atsushi; Hasegawa, Hirokazu*; Oshima, Yasuhiro*

no journal, , 

We propose a laser isotope separation utilizing difference of molecular rotational period, and experimentally demonstrate the principle, showing isotope selective ionization of N and N isotopologues. A linearly-polarized short laser pulse creates rotational wave packets in the isotopologues, which periodically revive with different revival times as a result of different moments of inertia. Another linearly-polarized short laser pulse ionizes one of the isotopologues preferentially, as a result of their different angular distributions and angular dependence of ionization probability. In the present experiment, the ion yield ratio R [= I(N)/I(N)] has been changed in the range from 0.85 to 1.22, depending on the time delay between the two laser pulses.

Isotope-selective ionization utilizing control of molecular rotation with femtosecond laser pulses; High selectivity with multiple pulse irradiation

Akagi, Hiroshi; Kasajima, Tatsuya*; Kumada, Takayuki; Itakura, Ryuji; Yokoyama, Atsushi; Hasegawa, Hirokazu*; Oshima, Yasuhiro*

no journal, , 

We are demostrating isotope-selective ionization of N and N isotopologues, utilizing molecular alignment and angular dependent ionization. In the present work, we used a train of four identical pulses with 125.7-ps interval to creating rotational wave packets in these isotopologues. The ion yield ratio N/N changed in the range from 0.49 to 2.00, which was two-times wider than that obtained with the single pulse.

Isotope-selective ionization utilizing molecular alignment of N isotopologues with a train of femtosecond laser pulses

Akagi, Hiroshi; Kasajima, Tatsuya*; Kumada, Takayuki; Itakura, Ryuji; Yokoyama, Atsushi; Hasegawa, Hirokazu*; Oshima, Yasuhiro*

no journal, , 

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.