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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.
Itakura, Ryuji; Ikuta, Tomoya*; Hosaka, Koichi*; Yokoyama, Atsushi; Yamanouchi, Kaoru*; Kannari, Fumihiko*
no journal, ,
Photoionization dynamics of ethanol in two-color (400 and 800 nm) intense laser fields is investigated using photoelectron-photoion coincidence spectroscopy. It is found that the fragment ion CHOH
is formed dominantly through the ionization to the electronically excited state by the 400-nm pulse when a 400-nm pulse and a 800-nm pulse are temporally separated. When a 400-nm pulse is temporally overlapped with a 800-nm pulse, the ionization to the electronically excited state by the 400-nm pulse is significantly suppressed, indicating that the ionization channel to the electronically excited state is closed due to the AC stark up-shift by the 800-nm pulse.
Kasajima, Tatsuya; Yokoyama, Keiichi
no journal, ,
Displacement of rotational-state distribution of diatomic molecules is studied as an example of coherent quantum control and to demonstrate the principle of a new scheme of isotope separation. The nitrogen molecules in the air are irradiated by a train of femtosecond laser pulses. The rotational-state distribution is measured to observed the effect of the irradiation. As a result, displacement of the rotational-state distribution has been confirmed. The degree of displacement agrees well with the theoretical prediction. The pulse train was made by a three-stage interferometer and a femtosecond Ti:S laser pulse. The rotational-state distribution was measured by the coherent anti-Stokes Raman scattering spectroscopy. However, the validity of applying the present method to coherent ensemble of molecules must be checked. Such experiments are planned.
8) caused by supersonic O
beamOkada, Ryuta; Yoshigoe, Akitaka; Teraoka, Yuden; Jinno, Muneaki*; Yamada, Yoichi*; Sasaki, Masahiro*
no journal, ,
Ge is one of the promising materials for the next generation FET because of its high carrier mobility overwhelming that of Si. Understanding of oxidation processes on Ge substrates with various index planes is necessary to control the quality of oxide layers for these devices. In this research, we employed SR-XPS to analyze oxide layers on the Ge(111)-c(28) surface formed by thermal-O gas and supersonic O beam. Ge
component was generated only by high energy supersonic O beam, although the oxide layer on Ge(100) has up to Ge
. This result indicates that oxidation states are different depending on crystal planes. Our results give insight into mechanisms of oxidation processes on Ge.
1 formed by supersonic O beamYoshigoe, Akitaka; Okada, Ryuta; Teraoka, Yuden; Jinno, Muneaki*; Yamada, Yoichi*; Sasaki, Masahiro*
no journal, ,
Ge has been attracted considerable attention as a new material of LSI because of its high carrier mobility. The O translational kinetic energy will be essential to understand the formation of oxide layers on Ge substrate for these devices. We previously reported that the high kinetic energy of the supersonic O beam enhances the oxidation on the Ge(100) at room temperature. In this research, we employed SR-XPS to analyze the oxidized Ge(100) surface formed by supersonic O molecular beam and back-filling O. In our experiments, we found the increase in amounts of the Ge oxide formed by supersonic O molecular beam comparing to that formed by back-filling O, although their coordination numbers were same in both cases. This result suggests that new oxygen adsorption states on the Ge(100) surface are activated by the supersonic O molecular beam. Our results give new knowledge concerning mechanisms of the formation of oxide layers on Ge substrate.