Optical Spectra Observed during Ion-Molecule Collisions Using Low-EnergyN2+andAr+Beams

A survey has shown that light emission from low-energy (< 1 keV) ion-molecule reactions is a common occurrence. ${\mathrm{Ar}}^{+}$ and $\mathrm{N}_2^{}{}_{}{}^{+}$ were used with target gases of Ar, ${\mathrm{H}}_2$, ${\mathrm{D}}_2$, CO, ${\mathrm{N}}_2$, ${\mathrm{O}}_2$, NO, ${\mathrm{N}}_2$O, C${\mathrm{O}}_2$, C${\mathrm{H}}_4$, and ${\mathrm{C}}_2$ ${\mathrm{H}}_2$; in addition, He, Ne, and Kr were used as $\mathrm{N}_2^{}{}_{}{}^{+}$ targets. Electronically excited states were produced by charge transfer and ionization with simultaneous excitation, conversion of translational to electronic energy of the incident ion or target, and dissociation with simultaneous excitation. For several collision partners, more than one of these reactions was seen. In general, charge-transfer reactions had the largest cross sections, to 2 × ${10}^{-16\mathrm{}}$ ${\mathrm{cm}}^2$, for ion laboratory energies of several hundred eV. Cross sections for the strongest features in the other types of reactions were about (1-5) × ${10}^{-17\mathrm{}}$ ${\mathrm{cm}}^2$.