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 H2 and H3+ in an ultra-short intense laser pulse by solving exactly the time-dependent Schrödinger 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 Rc in the singlet H2 and both the singlet and triplet states of H3+. Comparing the dynamics of H2 and that of H3+, 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.