STRONGLY MIXED RESONANCES IN THE PHOTOFRAGMENTATION OF HEBR2 NEAR BR-2(B) DISSOCIATION - STABILIZATION AND CLOSE-COUPLING STUDIES

The photofragmentation of the (HeBr2)-Br-79 van der Waals complex is s tudied for the transition from the ground to the excited electronic st ate B and where the Br-2 subunit is also excited to the neighborhood o f the nu(0)=45 vibrational state. At this vibrational level the bromin e molecule is close to its dissociation limit and the Delta nu=-1 chan nel is closed for dissociation of the complex. In a previous work it w as suggested that energy in the HeBr2(B, nu(0)=45) quasibound state ma y be internally redistributed (exciting van der Waals modes at the exp ense of the bromine excitation) prior to dissociation. Such mechanisms are more deeply studied in this work by means of the stabilization me thod, which works with square-integrable wave functions and is an appr opriate approach to perform quasibound state analysis. Stabilization t otal cross sections compare fairly well with close-coupling ones, wher e the proper asymptotic behaviour of the continuum wave functions is t aken into account. By inspection of the quasibound state wave function s, it is seen that energy is redistributed to several excited states b elonging to the nu(0)-1 manifold. In addition, it is shown that such e xcited states also carry oscillator strength in the transition from th e ground electronic state and thus interference effects in the excitat ion process are significant. HeBr2 near the halogen dissociation limit is found to be a rather strongly coupled system where the quasibound states involved can only approximately be assigned to quantum numbers corresponding to interhalogen and van der Waals vibrational excitation s. (C) 1997 American Institute of Physics.