Comparison of the mechanisms of enhanced ionization of H2 and H3+ in intense laser fields

The effects of spatial symmetry regulated by the molecular spin states on the ionization dynamics are investigated in two-electron molecular systems. As typical two-electron molecules, we focus on the ionization dynamics of H-2 and H-3(+) in an ultra-short intense laser pulse by solving exactly the time-dependent Schrodinger equation for a one-dimensional model which explicitly treats two electrons moving along the molecular axis on the assumption of fixed nuclei. Enhanced ionization is observed at a critical internuclear distance R-c in the singlet H-2 and both the singlet and triplet states of H-3(+). Comparing the dynamics of H-2 and that of H-3(+), it is clarified that not only the ionization potential of the molecule but also the spatial symmetry of the wave function has an important effect on the ionization dynamics. (c) 2007 Elsevier B.V. All rights reserved.