Theoretical study of the HPCl emission spectrum: re-assignment of the vibrational progressions and comparison with HNCl.
Résumé
An extended theor. anal. of the HPCl emission spectrum ~A(2A') → ~X(2A'') is reported in this study. Geometrical optimization and vibrational frequency calcns. are carried out at the DFT, CCSD(T) and CASPT2 levels. The Franck-Condon terms are evaluated beyond the harmonic approxn. from a variation-perturbation method. The spectrum simulation completes the previous assignments and underlines the presence of several overlapping progressions. An explanation of the splittings and shoulders obsd. on the main emission bands and non-investigated previously is proposed. The emission from the first 23 vibrational upper states has been examd. To complete this work, the HNCl ~A(2A') ~X(2A'') Franck-Condon terms are calcd. The resulting emission spectrum is compared to the HPCl one.