VIBRATIONAL PREDISSOCIATION DYNAMICS OF THE (HEBR2)-BR-79 VAN-DER-WAALS MOLECULE - A QUANTUM-MECHANICAL STUDY

The vibrational predissociation of the HeBr2 van der Waals complex is studied by means of bath accurate and approximate three dimensional qu antum mechanical calculations, Simple atom-atom potentials have been t ested for matching experimental measurements at low Br-2 vibrational e xcitations. The fragmentation dynamics when the bromine subunit is clo se to its B state dissociation limit is then explored and compared wit h experiments. For low to intermediate vibrational states v, good agre ement with most of the data (spectral shifts, lifetimes, average struc tures, average product energies) is achieved. The closing of the Delta v=-1 channel at v=44 and the binding energy at that position are succ essfully reproduced, although calculated and experimental blueshifts a nd linewidths are not in such good accordance in the v>38 range. For t hese high v excitations, fragmentation cross sections exhibit complica ted structures indicating strong interactions among different quasibou nd states. In addition, interesting threshold and intramolecular energ y redistribution effects are predicted. The closing of the Delta v=-1 channel is found to be a gradual process where different dynamical reg imes can be investigated in detail. (C) 1996 American Institute of Phy sics.