Ionization and dissociation of simple molecular ions in intense infrared laser fields: Quantum dynamical simulations for three-dimensional models of HD+ and H2+

The dynamics of multiphoton excitation of HD+ and H2+ in quasi-resonant infrared intense laser fields (I0 = 1.18 × 1014 W/cm2) is studied by the numerical solution of the time-dependent Schrödinger equations for the systems with explicit treatment of the nuclear vibrations and the electron motion beyond the Born-Oppenheimer approximation. It has been found, in particular, that on the time scale of 400 fs the overall ionization yield is about 40% for HD+, but only about 0.45% for H2+ while in accordance with the tunnel (or field) ionization mechanism at least comparable ionization yields could be expected for HD+ and H2+. The physical reason for this remarkable difference is that the nuclear motion is excited directly by the strong infrared laser field in HD+, but not in H2+.