A full quantum study of the vibrational predissociation mechanisms in Ar-3(+) cluster

The vibrational predissociation is investigated as a possible pathway of fragmentation for the Ar-3(+) cluster in its ground electronic state. The potential energy surface was computed before, using density functional methods, and includes all the relevant nuclear degrees of freedom. Around the energies of variationally calculated zero-order metastable levels, close-coupling equations describing dissociative continuum states were solved. The overlap between quasi-discrete and continuum wavefunctions allows, according to Fano's theory, a precise estimate of resonance energies and associated lifetimes. A dynamical approximation which diabatically select one specific vibrational level of the dimer core along the process and further makes use of the Fermi Golden Rule, the DGR approximation, is also employed. In this way, the effects on fragmentation times of vibrational excitation of the dimer ionic core and of the overall rotational temperature are investigated. We find that the averaged lifetimes of the metastable states obtained over a broad energy range decrease as the vibrational content of the core goes up. Furthermore, the calculations also confirm the tendency of the lifetimes to increase with the total angular momentum of the cluster, as surmised by the earlier experiments and calculations discussed in the main text. Both computational methods employed here confirm this tendency. (C) 1997 Elsevier Science B.V.