EXCITED-STATE FORMATION IN COLLISIONS BETWEEN SIMPLE IONS AND LI ATOMS

Excited-state formation in collisions of H+, He2+, He+, H2+, and He2+ ions with Li atoms has been studied in the kinetic energy range 5-1500 eV. Data were obtained by spectral analysis of near-uv-visible near-ir radiation resulting from spontaneous emission of excited species formed in the collisions. The dominant feature of all collision-produced spectra at all kinetic energies was the 670.8-nm LiI resonance line. Absolute emission cross sections for this line and a number of other spectral features as functions of ion kinetic energy are reported. Although there are no spin restrictions on the final states in the observed charge-transfer processes, only triplet HeI radiation was observed from He+-Li collisions. The absence of the corresponding HeI singlet is attributed to nearly inaccessible crossings of the He+(1 S2)-Li(2s S2) potential-energy curve with other singlet [HeLi]+ curves. The results for other collision systems are also discussed in terms of curve crossings. © 1979 The American Physical Society.