Quantum Reaction Dynamics Study Of The N + N₂ And OH + HBr Reactions In Gas Phase

In this paper, we carried out the quantum reaction dynamics studies of N + N2 and OH + HBr in gas phase. We have carried out a full dimensional degrees of freedom, time-dependent quantum reaction dynamics method to determine the energy efficiency in surmounting the reaction energy barrier of N + N2 and OH + HBr.We studied the N + N2 exchange reaction on the accurate ab initio potential energy surface reported by Wang and Stallcop et al. This potential energy surface shows two nonlinear transition states in the interaction region and a shallow well between these two barriers. Our results indicate that both the vibrational and rotational excitation of the reactant N2 hinder the reactivity. And, at an equal amount of total energy, the integral cross section ratios of the N-N first excited vibrational and rotational state over the ground-state display that the translational energy is much more effective in enhancing the reaction than the vibrational energy and rotational energy. Because the Polanyi rules don't involve the potential energy surface with a double barrier, and our study here on this double-barrier reaction adds further basic understanding on the energy efficiency roles for the atom-diatom reactions.For the OH + HBr reaction, we conducted a study on a newly published potential energy surface by Oliveira-Filho et al. It is worth mentioning that Oliveira-Filho et al. studied the OH + HBr reaction on this potential energy surface using quasiclassical trajectory calculations. In this paper, we firstly employed a six dimensional degrees of freedom, quantum reaction dynamics to study on the OH + HBr to determine which form of energy(translational energy,vibrational energy and rotational energy)initially deposited in reactants is the most effective one in surmounting the early barrier on the potential energy surface. And, this is the first to study the OH + HBr reaction by using a quantum time-dependent wave packet method. The calculations show that the vibrational motions of HBr and OH enhance the reactivity, while the HBr and OH's rotational motions significantly hinder the reactivity. And, for the OH + HBr reaction with a slightly early barrier, the vibrational energy in reactant raises the reactivity more effectively than the translational energy. Our results are contrast to the Polanyi rules, so Polanyi rules can not be simply extended for this four atomic reaction system. In addition, we also calculated the thermal rate constants over the temperature range 5-500 K and made a comparison with the available experimental data and theoretical calculations using quasiclassical trajectory calculations methods, our calculated thermal rate coefficients agree well with the results of previous.