Inelastic processes in ion-molecule collisions: ${\mathrm{Ar}}^{+}$ and ${\mathrm{He}}^{+}$ on ${\mathrm{N}}_2$ at low-keV energies

The ${\mathrm{Ar}}^{+}$ + ${\mathrm{N}}_2$ collision is studied at energies from 1.0 to 3.0 keV and in an angular range between 0 and 4.0 deg. The energy-loss spectra of the scattered ions demonstrate the presence of elastic scattering and inelastic processes arising from vibro-rotational excitation of the ground electronic state of ${\mathrm{N}}_2$, electronic excitation of the target with concomitant vibro-rotational excitation, and target ionization. Studies of the angular dependence of these processes suggest that (a) the collisions involve the entire molecule and are thus not adequately described in terms of a binary collision model, (b) electronic and vibrational excitation occur via mechanisms which exhibit negligible coupling, and (c) electronic excitation of ${\mathrm{N}}_2$ is due predominantly to the $B{}_{}{}^3{}_{}{}^{}\Pi _g^{}{}_{}{}^{}\to X{}_{}{}^1{}_{}{}^{}\Sigma _g^{+}{}_{}{}^{}$ transition as evidenced by observation of the onset of dissociation at larger scattering angles. The probability of charge exchange in ${\mathrm{Ar}}^{+}$ + ${\mathrm{N}}_2$ and ${\mathrm{N}}^{+}$ + ${\mathrm{N}}_2$ collisions is also investigated and shows an angular behavior very similar to that found in ${\mathrm{He}}^{+}$ + ${\mathrm{N}}_2$. Inelastic scattering results for ${\mathrm{He}}^{+}$ + ${\mathrm{N}}_2$ are reported.