Electronically excited states of molecular hydrogen exposed to strong direct current, alternative current, or low-frequency laser fields

Ionization rates and Stark shifts of electronically excited states of molecular hydrogen oriented parallel to an external electric or low-frequency electromagnetic field have been calculated within the fixed-nuclei approximation using a three-dimensional, fully correlated ab initio method. The investigation includes doubly excited autoionizing states. It is found that field-induced (avoided) crossings between different electronic states lead to a breakdown of simple models for predicting ionization rates.