An analysis of quasiclassical molecular collisions and rate processes for coupled vibration-dissociation and recombination

Abstract

Coupled molecular vibration-dissociation and recombination of oxygen highly diluted and suddenly heated in argon were solved using only microscopic information of molecules. Rate coefficients for state-to-state vibrational transitions and detailed dissociations were evaluated by quasiclassical molecular collision analysis using a sum of pairwise potentials of diatoms whereas those for detailed recombinations were estimated by the detailed balancing rule. Molecular vibration, dissociation, and recombination were described simultaneously by a set of master equations and solved using the rate coefficients. Quasisteady state dissociation rate coefficients, dissociation induction times, and vibrational relaxation times were calculated from the solutions and compared with experimental data so that the quantitative validity and features of the method could be assessed. The calculated steady state dissociation rate coefficients showed good agreement with the experimental values at temperatures above 3,000 K, whereas the calculated induction times and vibrational relaxation times were smaller than those from experiments. (Author) AbstractCoupled molecular vibration-dissociation and recombination of oxygen highly diluted and suddenly heated in argon were solved using only microscopic information of molecules. Rate coefficients for stateto-state vibrational transitions and detailed dissociations were evaluated by quasiclassical molecular collision analysis using a sum of pairwise potentials of diatoms whereas those for detailed recombinations were estimated by the detailed balancing rule. Molecular vibration, dissociation, and recombination were described simultaneously by a set of master equations and were solved using the rate coefficients. Quasisteady state dissociation rate coefficients, dissociation induction times, and vibrational relaxation times were calculated from the solutions and compared with experimental data so that the quantitative validity and features of the method could be assessed. The calculated steady state dissociation rate coefficients showed good agreement with the experimental values at temperatures above 3,OOOK, whereas the calculated induction times and vibrational relaxation times were smaller than those from experiments.

Models of Collisional Dissociation

“…Here v is the pre-collision vibrational quantum quantum level of the molecule and D indicates that the molecule becomes dissociated in the collision. The results are compared with the quasi-classical trajectory (QCT) results of Mizobata [7] for the O 2 -A system, as reported by Wysong and Wadsworth [8]. The agreement is not particularly good and, disappointingly, seems best for the original model, the results for the extended models having the wrong trend with vibrational level.…”

Quantal treatment of O2--Ar vibrational relaxation at hypersonic temperatures

“…This methodology of constructing the many-body potential energy surface is widely adopted for extensive quasi-classical studies of diatom and inert atom collisions. [21,22] The validity of this approach is based on the electronic structure of Ar ground electronic state, which has a closed-shell configuration [23]. The parameter values are given in Table 1.…”