Predissociation lifetimes of vibrational levels of the excited ? B? (Ka=O) electronic states of Cd ? H? and Cd ? D? complexes

The experimental rates of predissociation of vibrational levels of the ?B? (K'a-O) excited states of the Cd ? HZ and Cd ? D2 complexes are shown to be consistent with both semiclassical and quantum-mechanical pseudodiatomic theoretical treatments of the process. The ?B? pseudodiatomic potential was constructed by fitting an analytical function to the experimentally estimated Rydberg-Klein-Rees (RKR) inner and outer turning points. The potential of the repulsive ?A? state was estimated by fitting an exponential function to the ab initio points of Boatz, Gutowski, and Simons, then adjusting the exponential parameter slightly to maximize overall agreement with the observed Cd ? H? and Cd ? D? predissociation lifetimes. The best-fit repulsive curves for both the semiclassical and quantum-mechanism calculations result in slightly ?outer-wall? ?B?/?A? crossings at only 84 and 76 cm-?, respectively, above the ?B? potential minimum. The ?B??A? coupling matrix elements derived from both treatments were - 150-160 cm-?, much smaller than the 404 cm-?, expected if the spin-orbit interaction were unchanged from that of the asymptotic Cd(5s5p) states. It is suggested that the apparent reduction in the coupling strength could be due to the marked change in the nature of the Cd 5pa orbital due to the strong repulsive interaction with H, in the ?A? state and to the neglect of the anisotropy of the ?B??A? triatomic potential surface crossing.