Effects of an avoided crossing on linewidths of resonances in the H2 i3Π g state

Abstract

We have investigated the influence of nonadiabatic effects on the linewidths of quasi-bound rovibrational levels in the i3Πg state of molecular hydrogen. This state has a potential barrier due to the interaction of then=33Πg Rydberg series and the Q13Πg valence state. The radial coupling with the higher lying3Πg states has been modelled into a diabatic problem. The widths of thev=4 and 5 levels, a measure for their lifetimes, have been determined both in the adiabatic i3Πg potential, and in the two-state system. The results show small shifts of the i3Πg (v′=4,5;N′=1) levels of a few wavenumbers, and a significant increase of 49% in the lifetimes of these levels. Both effects are large enough to be important in spectroscopic experiments. The magnitude of the effect is in accordance with observed linewidths obtained in recent experiments. Model calculations for differently shaped potential barriers have been carried out to study the generality of the above conclusions.