Dissociative attachment and vibrational excitation in low-energy collisions of electrons withH2andD2

A semiempirical analysis is made of the contributions of the two lowest resonant states to dissociative attachment and vibrational excitation in low-energy collisions of electrons with ${\mathrm{H}}_2$ and ${\mathrm{D}}_2$. The resonance models are based both on ab initio calculations and on fits to experimental data. The dissociative-attachment cross section near threshold is enhanced significantly by vibrational or rotational excitation of the initial molecule. Near 10 eV, contributions from both resonances are required to explain the observed cross sections for vibrational excitation.