The electronic states of Ne2+, Ar2+, Kr2+, and Xe2+. II. Absorption cross sections for the 1(1/2)u→1(3/2)g, 1(1/2)g, 2(1/2)g transitions

Abstract

The lowest three dipole-allowed absorption bands in Ne2+, Ar2+, Kr2+, and Xe2+ are investigated using ab initio configuration interaction wave functions. Potential curves (reported in paper I) and transition moments (reported here) are obtained for Ar2+, Kr2+, and Xe2+ using the POL CI method. By shifting the Re of the 1(1/2)u state, the theoretical absorption profiles are normalized to the absolute cross sections of Lee and Smith and also Vanderhoff for the 1(1/2)u→2(1/2)g transition at (350.7 and 356.9) nm and 413.1 nm. The resulting absorption profiles are not only in good agreement with the remaining data of Lee and Smith, Vanderhoff, and Hunter for 1(1/2)u→2(1/2)g, but are also in good agreement with the experimental data of Lee et al. on the 1(1/2)u→1(1/2)g transition. The absorption profiles for Ne2+ are based on the ab initio potential curves and transition moments of Cohen and Schneider. The agreement with the few available cross sections of Lee and Smith is excellent. Comparison with the other theoretical calculations of the transition moments reveals the important effects of configuration interaction not included by Stevens et al. and the inaccuracies of the R/2 approximation employed by Michels. Finally, comparison with temperature dependent studies of Lee and Smith indicates much faster equilibration between the translational and vibrational degrees of freedom in Ne2+ than Ar2+.