Total cross sections for collisions ofH−andD−with various molecules

Absolute cross sections for electron detachment and charge transfer (or dissociative charge transfer) have been measured for collisions of ${\mathrm{H}}^{-}$ and ${\mathrm{D}}^{-}$ ions with ${\mathrm{N}}_2$, CO, ${\mathrm{O}}_2$, C${\mathrm{O}}_2$, and C${\mathrm{H}}_4$. The relative collision energies investigated range from a few eV up to several hundred eV. Electron detachment is found to be the dominant process for all the molecular targets except ${\mathrm{O}}_2$ for which charge transfer dominates. Isotope effects are observed in all the cross sections. 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. The general features of the charge-transfer cross section for the ${\mathrm{O}}_2$ target are in agreement with the ideas of a simple two-state collision model. The cross sections for charge transfer (or dissociative charge transfer) are found to be small for all targets except ${\mathrm{O}}_2$.