Dissociation ofN2+andO2+by Electron Impact

Cross sections for dissociation of ${\mathrm{N}}_2^{+}$ and ${\mathrm{O}}_2^{+}$ by electron impact were measured for interaction energies $E$ between 10 and 500 eV and between 15 and 500 eV, respectively. The cross-section-versus-interaction-energy curves exhibit maxima in the vicinity of 75 eV and decrease monotonically at higher energies with an ($\frac{A}{E}$) $log\mathrm{BE}$ dependence. Maximum cross-section values are $4.3\pi {a_0}^2$ for ${\mathrm{N}}_2^{+}$ and $4.1\pi {a_0}^2$ for ${\mathrm{O}}_2^{+}$. The curves are remarkably similar at the higher interaction energies. The ion targets are typical of those formed by bombardment of gas by electrons of 150 eV and more, and some may be in excited electronic states.