title: Dynamical regimes on the Cl + H2 collisions: inelastic rainbow scattering.
abstract: While Cl + H(2) reactive collisions have been a subject of numerous experimental and theoretical studies, inelastic collisions leading to rotational energy transfer and/or vibrational excitation have been largely ignored. In this work, extensive quantum mechanical calculations covering the 0.5-1.5 eV total energy range and various initial rovibrational states have been carried out and used to perform a joint study of inelastic and reactive Cl + H(2) collisions. Quasiclassical trajectories calculations complement the quantum mechanical results. The analysis of the inelastic transition probabilities has revealed the existence of two distinct dynamical regimes that correlate with low and high impact parameters, b, and are neatly separated by glory scattering. It has been found that while high-b collisions are mainly responsible for |Δj| = 2 transitions which dominate the inelastic scattering, they are very inefficient in promoting higher |Δj| transitions. The effectiveness of this type of collision also drops with rotational excitation of H(2). In contrast, reactive scattering, that competes with |Δj| > 2 inelastic transitions, is exclusively caused by low-b collisions, and it is greatly favored when the reactants get rotationally excited. Previous studies focusing on the reactivity of the Cl + H(2) system established that the van der Waals well located in the entrance channel play a key role in determining the mechanism of the collisions. Our results prove this to be also a case for inelastic processes, where the origin of the double dynamical regime can be traced back to the influence exerted by this well that shapes the topology of the entrance channel of the Cl-H(2) system.
authors.affiliation: Grupo de Dinámica Molecular, Departamento de Química Física, Facultad de Química, Universidad de Salamanca, 37008 Salamanca, Spain.
authors.forename: L
authors.initials: L
authors.lastname: González-Sánchez
authors.forename: J
authors.initials: J
authors.lastname: Aldegunde
authors.forename: P G
authors.initials: PG
authors.lastname: Jambrina
authors.forename: F J
authors.initials: FJ
authors.lastname: Aoiz