Theoretical Study Of The Dynamics For The S（³P）+H₂Reaction

The reaction S+H2plays an important role in combustion and atmospheric chemistry asa simplest reaction involving sulfur atoms and a prototype for hydrogen-atom abstractionreaction, especially it is one of the chief culprits of acid rain, air pollution, and global climatechange. In the past studies, more attention were focused on the electronic excitation effect onthe reaction dynamic of atomic sulfur and the possible role of intersystem crossing betweentriplet and singlet potential surface. Up to now, there is almost no study on the stereo-dynamicinformation of S(3P)+H2reaction. So, investigating the stereodynamics properties of thereaction has extremely important significance. In order to explore more details of S+H2reaction system, we performed quasi-classical trajectory (QCT) studies based on the preciseab-initio potential energy surface (PES) presented by Lv et al. We investigated itsstereodynamics properties, as well as the collision energy, vibrational and rotational excitationand isotopic influences on the stereodynamics. The PES is a repulsive surface because therepulsive energy released in the exit channel. In this work, we proposed reasonableexplanations by the analysis of calculation results and the topology characteristics of the PES.Firstly, we investigated the influences of collision energy on the dynamics properties ofthis reaction. It has been found, our QCT reaction probabilities and cross sections are in goodagreement with the previous QM results which presented by Lv et al. The collision energysignificantly enhances the reaction probabilities and cross sections. The scattering directionevolves from the backward scattering to the sideway scattering with increasing the collisionenergy. The product SH exhibits a rather strong alignment perpendicular to the scattering z-xplane and a strong orientation pointing to the negative y-axis. Moreover, the bigger thecollision energy is, the weaker the alignment and orientation of the product are.In addition, we studied the effect of reagent H2rovibrational excitation on the dynamicsproperties of the title reaction. The result illustrates that the alignment degree of the productdecrease with the increase of j or v, besides, the rotation of the product HS has a preference ofchanging from the in-plane reaction mechanism to the out-of-planes mechanism withincreasing the reagent rovibrational excitation. The title reaction tends to the backwardscattering as j increases from0to3, however, the title reaction changes from theside-backward scattering to the forward scattering as v increases from0to3. Finally, we studied the vector corrections between reagents and products for S+H2, S+D2, and S+T2reactions. The result illustrates that the degree of sideward scattering becomesweaker and backward scattering becomes stronger as the mass of the reagent increases. Foreach of the reactions, the products rotational angular momentum vector j’ is strongly alignedalong the direction perpendicular to k, the alignment is found to be stronger in the heaviermass isotope system. Moreover, all the j’ orientation along the opposite direction of the y axis,the isotope mass effect becomes stronger as the mass of the reagent increases..In this work, we found some interesting phenomena and given reasonable explanationsof them. These results enriched the theory study of the stereo-dynamics about S(3P)+H2reaction.