The impact-parameter method is used to calculate integral cross sections for electronic excitation and dissociation of ${\mathrm{O}}_2$ and ${\mathrm{S}}_2$ by electron impact. For both molecules, excitations to bound and dissociative states are considered for transitions from the ground electronic state (X ${\mathrm{}}^3$${\Sigma }_g^{\mathrm{-}}$) to the two lowest states of ${}_{}{}^3{}_{}{}^{}\mathrm{\Sigma }_{\mathrm{u}}^{\mathrm{-}}{}_{}{}^{}$ symmetry (labeled B and E for ${\mathrm{O}}_2$ and B and 2 for ${\mathrm{S}}_2$) and the lowest state of ${}_{}{}^3{}_{}{}^{}\mathrm{\Pi }_{\mathrm{u}}^{}{}_{}{}^{}$ symmetry. The dependence of the cross sections upon initial vibrational and rotational states is studied for low collision energies (threshold to 25 eV). For some transitions a change in initial vibrational state can have a significant effect upon the cross sections, but, in general, the effect of changing the initial rotational state is small.

• Received 26 December 1984

DOI:https://doi.org/10.1103/PhysRevA.32.3366