Molecular laser isotope separation without tunable lasers; Isotope-selective ionization of N isotopologues using femtosecond laser-induced molecular alignment

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

We propose a laser isotope separation method without tunable lasers, and demonstrate isotope selective ionization of nitrogen isotopologues. This method is based on molecular alignment and angular dependent ionization. A non-resonant femtosecond (fs) laser pulse with a linear polarization creates rotational wave packets in the isotopologues. These wave packets periodically exhibit aligned and antialigned distributions at specific time delays. At a specific time delay when one isotopologue is aligned and the other one is anti-aligned, another non-resonant linearly-polarized fs laser pulse (ionization pulse) ionizes the aligned isotopologue preferentially via the non-resonant multiphoton ionization, because of angular dependence of the N ionization probability. The ion yield ratio R [= I(N) / I(N)] depends on the time delay, ranging from 0.68 to 1.41.