Energy-Loss Spectra and Collision Cross Sections for Impact of 20-120-keV Positive Ions on Molecular Nitrogen

Inelastic energy-loss spectra induced by impact of ${\mathrm{H}}^{+}$, ${\mathrm{H}}_2^{+}$, and ${\mathrm{Ar}}^{+}$ on ${\mathrm{N}}_2$ have been measured at incident ion energies of 20-120 keV, with an energy resolution of about 2 eV. Prominent peaks are observed at energy losses of 9.5 and 13.8 eV. The first of these is well resolved and is attributed to excitation of the Lyman-Birge-Hopfield (LBH) system of ${\mathrm{N}}_2$. The peak at 13.8 eV is believed due primarily to excitation of the $b{}_{}{}^1{}_{}{}^{}\pi _u^{}{}_{}{}^{}$ band of the Worley-Jenkins series. The locations of these features on the energy-loss scale do not agree with results of the electron impact work of others and, in general, show trends with projectile velocity that are consistent with an assumed enhancement of excitation to higher vibrational states with the heavier particles. Collision cross sections for excitation of the two peaks are presented, as well as the total ionization cross section and the cross section for total inelastic processes in the case of proton impact.