A time-dependent wave packet study of the H4 four-center reaction

A quantum model based on the time-dependent initial state selected wave packet approach was developed to study the four-center (4C) reaction, A2 + B2 → 2AB, and the competing collision induced dissociation (CID), A2 + B2 → A + B2 + A, as applied to the H2(v1) + H2(v2) 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 A2 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 A2 diatom, the 4C process is dominant; as the A2 diatom becomes highly excited the CID process becomes more important at low collision energies with B2, but as the collision energy increases the 4C process is favored again.