Photoionization of homonuclear diatomic molecules aligned by an intense femtosecond laser pulse

Abstract

We calculated the photoelectron angular distribution (PAD) expected in the laboratory frame (LF PAD) for the ionization of ${\mathrm{N}}_{2}$ molecules that are aligned by an intense laser pulse. We consider two independent processes of the dynamical alignment of molecules in the electronic ground state by an intense femtosecond laser pulse $(>10\phantom{\rule{0.3em}{0ex}}\mathrm{TW}∕{\mathrm{cm}}^{2})$ and one-photon ionization or $(2+1)$ resonance-enhanced multiphoton ionization of the aligned molecules by a weak laser pulse $(<10\phantom{\rule{0.3em}{0ex}}\mathrm{GW}∕{\mathrm{cm}}^{2})$. We examined the variation of the LF PAD against the intensity of the alignment laser, durations of the alignment and ionization laser pulses, and the time delay between these pulses. The LF PAD obtained from the ionization of the aligned ensemble shows a semiquantitative agreement with the PAD in the molecular frame.