Molecular hydrogen exposed to a suddenly turned-on strongelectric field or low-frequency laser

Abstract

The behaviour of molecular hydrogen in a dc or (low-frequency)laser field is studied in the limit of a sudden switch-on of thefield. Compared to the case of an adiabatically slow turn-on itis found that around the equilibrium internuclear distance thepopulation of the adiabatic ground state remains dominant evenfor very strong fields. However, this picture changes atinternuclear distances corresponding to field-induced (avoided)crossings with an excited state. At these distances the groundand excited states are populated with similar probabilities. Itis concluded that even in the limit of an instantaneous turn-onof the field it is sufficient to consider the ionization rate ofat most two electronic states.