Electron detachment for collisions ofH−andD−with hydrogen molecules

Abstract

Absolute total cross sections for electron detachment and the production of slow product ions have been measured for collisons of ${\mathrm{H}}^{\ensuremath{-}}$ and ${\mathrm{D}}^{\ensuremath{-}}$ ions with ${\mathrm{H}}_{2}$, ${\mathrm{D}}_{2}$, and HD. The threshold behavior of the detachment cross section for the above reactants has been determined in experiments in which the relative collision energies range from about 1 eV up to several hundred. The thresholds for detachment for both ${\mathrm{H}}^{\ensuremath{-}}$ and ${\mathrm{D}}^{\ensuremath{-}}$ ions are found to be larger than the electron affinity. Isotopic substitution reveals that the detachment cross sections scale with relative collision energy at low collision energies and with relative collision velocity at high collision energies. Upper and lower bounds on detachment-rate constants which are based upon the measurements are presented.