Spontaneous dissociation and rovibrational structure of the metastable D2− anion

Abstract

Long-lived rovibrational states of the metastable ${{\mathrm{D}}_{2}}^{\ensuremath{-}}$ molecular anion, with lifetimes of the order of microseconds, were studied by recording the time-of-flight difference between D and ${\mathrm{D}}^{\ensuremath{-}}$ fragments produced by spontaneous dissociation of the ${{\mathrm{D}}_{2}}^{\ensuremath{-}}$ complex. The simulated time-of-flight spectrum was adjusted to the experimental results, allowing us to extract the resonance energy relative to the dissociation threshold. A single value was found, $22.8\ifmmode\pm\else\textpm\fi{}0.3$ meV, which is somewhat larger than resonance energies predicted by theory for long-lived ${{\mathrm{D}}_{2}}^{\ensuremath{-}}$ rovibrational states with $(J,v)$ quantum numbers (37,0), (37,1), and (38,0) [Phys. Rev. A 75, 012507 (2007)]. This discrepancy seems due to the extreme sensitivity of these metastable states to minute features of the potential energy curve. The spectral feature is explained by the competition between autodetachment and spontaneous dissociation decay channels.