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isotopologues with a train of femtosecond laser pulsesAkagi, 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.
Saeki, Morihisa; Matsumura, Daiju; Yomogida, Takumi; Taguchi, Tomitsugu; Tsuji, Takuya; Kusano, Shogo*; Miyazaki, Tatsuya*; Takao, Koichiro*; Oba, Hironori; Nakashima, Nobuaki*
no journal, ,
no abstracts in English
Shiga, Motoyuki; Ruiz-Barragan, S.*; Ishimura, Kazuya*
no journal, ,
With the advent of massively parallel computer, there is a need for theoretical methods and calculation algorithm that can derive its maximum performance. Among the ones being suitable for parallel computing, there is a class of molecular simulation methods that performs the force calculations simultaneously for different molecular structures of the same system. Such molecular simulation methods are diverse depending on the purpose, but many of them have been established using classical force field. However, as the computing power increases in the future, it is expected that ab initio simulations based on first-principles electronic structure calculation would also become feasible. Here, the technical problem is to perform simultaneously a replica parallel for the first-principles calculation code that has already been parallelized. In this study, we establish such a hierarchical parallel computing techniques and develop an interface code, PIMD.
Kurosaki, Yuzuru; Yokoyama, Keiichi
no journal, ,
no abstracts in English