Ion-Impact Excitation of Pure Vibrational Transitions in Diatomic Molecules

An ion-impact spectrometer has been constructed to measure the energy loss of ions inelastically scattered without charge exchange from molecular targets. Pure vibrational transitions excited by ${\mathrm{H}}^{+}$ and ${\mathrm{H}}_2^{+}$ projectiles of energies from 100 to 600 eV have been observed in ${\mathrm{H}}_2$, ${\mathrm{D}}_2$, and ${\mathrm{N}}_2$. The angular distribution of scattered ions and the energy dependence for these processes have been investigated. The excitation cross sections for pure vibrational transitions are unusually large.