A FULL QUANTUM STUDY OF THE VIBRATIONAL PREDISSOCIATION MECHANISMS INAR-3(+) CLUSTER

The vibrational predissociation is investigated as a possible pathway of fragmentation for the Ar-3(+) cluster in its ground electronic stat e. The potential energy surface was computed before, using density fun ctional methods, and includes all the relevant nuclear degrees of free dom. Around the energies of variationally calculated zero-order metast able levels, close-coupling equations describing dissociative continuu m 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 approximat ion which diabatically select one specific vibrational level of the di mer core along the process and further makes use of the Fermi Golden R ule, the DGR approximation, is also employed. In this way, the effects on fragmentation times of vibrational excitation of the dimer ionic c ore and of the overall rotational temperature are investigated. We fin d that the averaged lifetimes of the metastable states obtained over a broad energy range decrease as the vibrational content of the core go es 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 t he main text. Both computational methods employed here confirm this te ndency. (C) 1997 Elsevier Science B.V.