Quasi-classical trajectories study of Ne79Br2(B) vibrational predissociation

Abstract

A full-dimensional quasi-classical trajectories study on the vibrational predissociation (VP) of the Ne⁷⁹Br₂(B) complex is presented. Following the most recent experiments, the Br₂(B) vibrational levels v′ = 16–29 were explored. The total angular momentum, J, was taken to be zero, and a semiclassical Franck–Condon model to compute initial conditions from quantum distributions was employed. Predissociation lifetimes were extracted from Ne⁷⁹Br₂ population decay by using two different exponential laws. Predicted lifetimes are in excellent agreement with the last experimental results [J. A. Cabrera, C. R. Bieler, B. C. Olbricht, W. E. van der Veer and K. C. Janda, J. Chem. Phys., 2005, 123, 054311]. The Br₂ fragment ro-vibrational distributions resulting from the VP of the molecule were obtained from the statistics of classical magnitudes using the standard binning procedure. Computed rotational distributions (for the Δv′ = −1, −2 channels) are also in very good agreement with the experimental results [M. Nejad-Sattari and T. A. Stephenson, J. Chem. Phys., 1997, 106 5454]. The influence of two quantum effects—the closing of the Δv′ = −1 dissociation channel and the intramolecular vibrational relaxation (IVR) mechanism—on the agreement with experimental rotational distributions, is discussed. Due to the classical character of our calculations and the binning procedure we used, the agreement of computed vibrational distributions with experimental and quantum theoretical is qualitative. For instance, for v′ = 28—for which the Δv′ = −1 channel is experimentally found to be closed—the Δv′ = −2 channel becomes statistically more significant. A discussion on the viability of similar quasi-classical methods to model the VP dynamics of analogous clusters is presented.