Phase control of molecular ionization: H-2(+) and H-3(2+) in intense two-color laser fields

Charge resonance-enhanced ionization is examined for combinations of intense, linearly polarized laser fields, and their second harmonic (1 omega-2 omega) for both a diatomic molecular ion (H-2(+)) and an asymmetric linear triatomic molecular ion (H-3(2+)). Ionization is found to be strongly dependent on the relative phase between the tow colors in both cases. In particular for H-2(+) one can achieve nearly complete ionization of electrons at one of the nuclei only. For the asymmetric linear triatomic molecular ion (H-3(2+)) enhanced ionization is shown also to occur at large critical distances. In the presence of two color fields, the ionization rate of the asymmetric H-3(2+) can be controlled again by tuning the relative phase between the driving fields. The phase control of the enhanced ionization can be rationalized in terms of field-induced over-the-barrier ionization and laser-induced electron localization or equivalently electron tunneling suppression.