EFFECTS OF AN AVOIDED CROSSING ON LINEWIDTHS OF RESONANCES IN THE H(2)I(3)PI (G) STATE

We have investigated the influence of nonadiabatic effects on the line widths of quasi-bound rovibrational levels in the i(3) Pi(g), state of molecular hydrogen. This state has a potential barrier due to the int eraction of the n = 3 (3) Pi(g) Rydberg series and the Q1 (3) Pi(g), v alence state. The radial coupling with the higher lying (3) Pi(g), sta tes has been modelled into a diabatic problem. The widths of the upsil on = 4 and 5 levels, a measure for their lifetimes, have been determin ed both in the adiabatic i(3) Pi(g), potential, and in the two-state s ystem. The results show small shifts of the i(3) Pi(g)(upsilon' = 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 b e important in spectroscopic experiments. The magnitude of the effect is in accordance with observed linewidths obtained in recent experimen ts. Model calculations for differently shaped potential barriers have been carried out to study the generality of the above conclusions.