Breakup ofH2+by one photon in the presence of a strong dc field

Abstract

We calculate the frequency profile of the rate for breakup of ${\mathrm{H}}_{2}^{+}$ by one photon in the presence of a strong dc field. After photoexcitation of the molecular ion from its ground $1s\ensuremath{\sigma}$ electronic state to the $2p\ensuremath{\sigma}$ electronic state, the nuclei are temporarily trapped by a dc field-induced barrier with turning point ${R}_{\mathrm{max}}.$ However, the nuclei are released through either rotation of the internuclear axis (which, for the sake of tractability, we ignore) or dc-field ionization involving resonant transfer from the $2p\ensuremath{\sigma}$ state to a more highly excited state. The most prominent resonance occurs at an internuclear separation that is less than ${R}_{\mathrm{max}}$ and, in a.u., is approximately ${3/(8F}_{\mathrm{dc}})+3,$ where ${F}_{\mathrm{dc}}$ is the dc field strength. We interpret the change in the frequency profile, as ${F}_{\mathrm{dc}}$ varies, in terms of different aspects of the dynamics of the breakup process, in particular the dispersion of the probability distribution of the nuclei due to over-the-barrier dissociation from the $1s\ensuremath{\sigma}$ state.