A theoretical study on electronic predissociation in the NeBr 2 van der Waals molecule

We present the first comprehensive ab initio study of the Ne-Br 2 potential energy surfaces and the non-adiabatic couplings between the valence excited electronic states. These ab initio results are used to obtain 3-D approximate potentials for each electronic state, and these potentials are used in a wave packet calculation of the competing electronic predissociation and vibrational predissociation dynamics. The results of this calculation are in excellent agreement with both experimental results and a previous empirical fit to the experiments. The calculations allow us to observe not only the competition between vibrational and electronic dynamics for the dimer, but also the competition between two different electronic channels. Coupling to the 2 g state dominates for the levels studied here, but coupling to the C state is progressively more important for low vibrational levels, and may dominate at levels below which the current results pertain. The ability of ab initio surfaces and couplings to so accurately reproduce experimental data raises the hope of a complete understanding of the VP and EP dynamics for other Rg-halogen dimers. Success in the case presented here is largely due to the fact that the VP dynamics for the vibrational levels in this study are in the simple, direct regime. Understanding the simple case so thoroughly provides new hope that the more complicated examples, such as ArI 2 and NeCl 2, for which experiment and theory are not currently in accord, may yet yield to analysis. © 2011 Elsevier B.V. All rights reserved.This work has been supported by the Ministerio de Ciencia e Innovación under grants CSD2009–00038 (programa CONSOLIDER-INGENIO 2010 entitled “Molecular Astrophysics: the Herschel and Alma era”), and FIS2010-18132, US National Science Foundation Grant CHE-0911686.Peer Reviewe