Vibrational dependence of negative-ion formation by dissociative attachment of low-energy electrons

The vibrational dependence of dissociative attachment in low-energy ${\mathrm{Na}}_2$(v’ ’)+${\mathit{e}}^{\mathrm{-}}$ collisions (${\mathit{E}}_{\mathit{e}\mathit{l}}$${\mathrm{Na}}_2$ vibrational distribution is controlled through Franck-Condon pumping. A range of vibrational levels with energies up to approximately 60% of the molecular binding energy is covered. We observe a three orders of magnitude increase in the dissociative attachment rate for low lying and intermediate vibrational levels v’ ’. Further analysis shows a strikingly abrupt leveling off above v’ ’≊12.