Phase control of molecular ionization: H2 + and H3 2+ in intense two-color laser fields.

Abstract

Charge resonance-enhanced ionization is examined for combinations of intense, linearly polarized laser fields, and their second harmonic (1\ensuremath{\omega}-2\ensuremath{\omega}) for both a diatomic molecular ion (${\mathrm{H}}_{2}$${\mathrm{}}^{+}$) and an asymmetric linear triatomic molecular ion (${\mathrm{H}}_{3}$${\mathrm{}}^{2+}$). Ionization is found to be strongly dependent on the relative phase between the two colors in both cases. In particular for ${\mathrm{H}}_{2}$${\mathrm{}}^{+}$ one can achieve nearly complete ionization of electrons at one of the nuclei only. For the asymmetric linear triatomic molecular ion (${\mathrm{H}}_{3}$${\mathrm{}}^{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 ${\mathrm{H}}_{3}$${\mathrm{}}^{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. \textcopyright{} 1996 The American Physical Society.