Seminar by Jesús Rubayo-Soneira (INSTEC, Havana, Cuba)

Professor Jesús Rubayo-Soneira (INSTEC, Havana, Cuba) will give a seminar entitled "Photofragmentation dynamics study of van der Waals clusters using two theoretical methods: quasiclassical trajectories and trajectory surface hopping"

Résumé:

Ideally, dynamic calculations provide the most detailed information about end-state distributions in collision or semi-collision processes. In this sense, it is often the case that practical drawbacks severely restrict the application of intrinsically accurate quantum calculations, which is particularly a problem if large clusters are to be studied. In most cases, however, quasi-classical methods exhibit a relatively high interpretive power / computational cost ratio and allow the full dimensionality of the system to be included. However, although quasi-classical calculations are important for constructing intuitive models of molecular processes, the limits of their validity and applicability remain uncertain.
During the last two decades, the van der Waals complex has been the subject of intense investigation from both experimental and theoretical points of view. In this work, we show how a very good description of the available data can be achieved by conducting a study of full-dimension quasi-classical trajectories on the process in electronic molecular states. The influence of two quantum effects such as the dissociation channel closure and the intramolecular vibrational relaxation (IVR) mechanism on the agreement with experimental rotational distributions. A discussion is presented on the feasibility of similar quasi-classical methods to model VP dynamics.
The vibrational predissociation of RG^- (I₂ and Br₂), has been studied using a variety of theoretical and experimental methods, producing a large number of results. Therefore, it is a useful system to compare different theoretical methods. We apply the methods of quasiclassic trajectories and surface trajectories (TSH). The dynamics of the system was propagated on a potential energy surface (PES) corresponding to quantum molecular vibrational states with the possibility of jumping towards other surfaces until the van der Waals bond dissociates. This allows adding quantum vibrational effects to a classical dynamics approach.
We have also incorporated the kinetic mechanism for a better understanding of the evolution of the complex.
The novelty of this work is that it allows us to incorporate all the surfaces into the dynamics of the system. The calculated half-lives are similar to those reported experimentally. The rotational distribution, the rotational energy are also calculated and compared with the experiments.