Molecular rotation in strong-field ionization

A detailed vibrationally and rotationally resolved study for the fragmentation dynamics of the hydrogen molecular ion (${{\text{H}}_{2}}^{+}$) under intense short laser pulses is presented. Our theoretical nonadiabatic quantum molecular dynamics approach allows us to dynamically include all degrees of freedom for ionization also. We find that in general rotation enhances ionization compared to that in rotationally frozen molecules, with a weaker effect on highly vibrationally excited states. We identify the alignment time of one-quarter of the rotational period as the parameter which decides the dynamical relevance of rotation. Our analysis explains the dominance of dissociation over ionization observed experimentally and also clarifies why dimensionally reduced calculations predict a dominance of ionization.