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 Deltav'=-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 Deltav'=-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 Deltav'=-1 channel is experimentally found to be closed-the Deltav'=-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.

Quasi-classical trajectories study of Ne2Br2(B) vibrational predissociation: Kinetics and product distributions

“…This effect has been observed in the experiment 47 and is reproduced by our QCT calculations, as seen by comparing the corresponding lifetimes in Table II with the QCT predictions in Table 1 of Ref. 31.…”

“…The initial and final distributions have, nevertheless, similar shapes. Although experimental rotational distributions were not reported in the experiment 47 , a few points can be made with respect to QCT predictions: (a) the Boltzmann-like shape seems to be consistent with experimental measurements for the directly excited NeBr 2 molecule 14 , and previous QCT calculations 31,35 ; and (b) the Br 2 product is more rotationally excited than in the photo-dissociation of NeBr 2 14,31,35 , for which the distributions peak about j f = 4-6. The extent of the QCT distributions may be expected to differ from future experimental measurements due to the PES employed (see discussion at the end of Sec.…”

“…62. Then, the X-state wave function is used to calculate the probability distributions (statistical weights) for all relevant variables, while the eigenvalues from the B-state determine the VP energetics, as in our previous work 31,35 . Once the X-and B-state quantum problems are solved, QCT initial conditions are calculated following the algorithm proposed in Ref.…”

Cartesian coupled coherent states simulations: NenBr2 dissociation as a test case

“…In the classical simulations of González-Martínez et al, 7 the initial configurational energies (i.e., the sum of the kinetic and potential energies) include an extra contribution due to the zero point energy of the complex. In the classical simulations of González-Martínez et al, 7 the initial configurational energies (i.e., the sum of the kinetic and potential energies) include an extra contribution due to the zero point energy of the complex.…”

“…[4][5][6][7][8][9][10][11][12][13] Although there are many studies involving the triatomic complex, it is much more difficult to study the a) Electronic mail: S.K.Reed@physics.org. Some preliminary results are also presented for the tetra-and penta-atomic clusters, Ne 2 Br 2 and Ne 3 Br 2 .…”