Molecular ion-pair states in ungerade H2

Abstract

Molecular ion-pair states are analogs of electronic Rydberg states, but with the electron replaced by a much heavier ion. We calculate ab initio the long-range vibrational H${}^{+}$H${}^{\ensuremath{-}}$ ion-pair states in H${}_{2}$ for ungerade ${}^{1}{\ensuremath{\Sigma}}_{u}^{+}$ symmetry, corresponding to recent observations by Ekey and McCormack [Phys. Rev. A 84, 020501 (2011)]. The overall trends in the experiment are reproduced and many peaks can be assigned. The calculations yield interloper resonances corresponding to vibrational states trapped inside the barriers on the potential-energy curves 5,6$\phantom{\rule{0.16em}{0ex}}{}^{1}{\ensuremath{\Sigma}}_{u}^{+}$.