Measurement of branching ratios for the dissociative recombination of cold HD+ using fragment imaging.

Two-dimensional fragment imaging is used to determine branching ratios into final atomic states for dissociative recombination of vibrationally cold ${\mathrm{HD}}^{+}$ molecules with electrons at variable energy. For low electron energies it is found that the dissociation proceeds via the $^{1}\ensuremath{\Sigma}_{g}^{+}$ state, leaving one of the fragments in the $n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2$ level. At higher energies up to $\ensuremath{\approx}20\mathrm{eV}$, a pronounced angular anisotropy of the fragmentation is found on one of the previously measured resonances, allowing for conclusions about the symmetry of the dissociating states.