A time-dependent wave packet study of the H 4 four-center reaction

Abstract

A quantum model based on the time-dependent initial state selected wave packet approach was developed to study the four-center (4C) reaction, A 2 + B 2 → 2AB, and the competing collision induced dissociation (CID), A 2 + B 2 → A + B 2 + A, as applied to the H 2(v 1) + H 2(v 2) system important in combustion. A reduced three-dimensional model of the reaction with the atoms constrained to an isosceles trapezium and a realistic global potential energy surface of Aguado et al. [J. Chem. Phys. 101 (1994) 2742], following Hernández and Clary [J. Chem. Phys. 104 (1996) 8413], was used. A method to analyse the reaction flux for 4C and CID reaction probabilities is presented. The initial A 2 vibrational excitation is not only more efficient than translational energy in facilitating the 4C and CID processes, it also reduces the threshold energy. Both the 4C and CID processes exhibit similar threshold energy behavior. For low vibrational excitation in the A 2 diatom, the 4C process is dominant; as the A 2 diatom becomes highly excited the CID process becomes more important at low collision energies with B 2, but as the collision energy increases the 4C process is favored again. © 2004 Elsevier B.V. All rights reserved.