Theoretical Study Of The Dynamics For The Reaction H+LiH

In astrophysics,the Li H molecule has been the subject of researchers’ attention.According to the big bang nucleosynthesis model,the early universe is very simple,only containing the simple nuclear H/D/He/Li,electrons and low-energy photons.The LiH molecule,which is composed of Li atom and an H atom,is considered to be among the earliest formed molecules,and is the carrier of high dipole moment.According to the study by Dubrovich et al.,it is found that molecules with high dipole moments,are more likely to leave their imprint in the cosmic radiation background.In order to investigate the evolution of the universe,researchers are interested in the formation and consumption of LiH molecules.It is generally believed that the LiH molecule is formed by Radiation Association,and consumed by the high-speed collision with H atoms.This paper showed that the dynamic of consumption process of H+Li H reaction,obtained by using the quasi classical trajectory method,based on the potential energy surface of Chen et al.The effects of collision energy,ro-vibrational excitation and isotope effect on the dynamic of reaction were studied.Firstly,we calculated the dynamic properties of the reaction with different collision energies.The results showed that the collision energy had a profound influence on both the scalar and vector properties of the reaction.Because there is no threshold on the potential energy surface,the reaction probability [P（b）] and reaction cross section（ICS）showed a decreasing trend.At the low collision energy range,the degree of polarization of product H₂ and orientation effects were weakened as collision energy increased,while the polarization degree of H₂ and orientation effect was the opposite of the trend as collision energy increased in the high collision energy range.The reaction was mainly dominated by the direct reaction mechanism,and formed the short life complex at the low collision energy.The product H₂ molecule was mainly dominant by the forward scattering,and the degree increased with the increase of the collision energy.Secondly,we considered the effect of the vibrational quantum number on the dynamics of the reaction.As the collision energy is 0.6eV,we calculated the reactionprobability,cross section and polarization distribution of product rotational angular momentum j’ when the vibrational quantum number v is 0,3,6 and 9,respectively.It is noted that the reaction probability and the reaction cross section of the LiH consumption channel of the H+Li H reaction were suppressed when the vibration excitation of the reactants enhanced,while the probability and cross section of the H atom exchange channel was promoted.With the increase of the vibration excitation of the reactant,the polarization degree and the orientation effect of the product rotational angular momentum were weakened.However,the degree of polarization and the orientation effect of the rotational angular momentum of the H₂ molecule suddenly increased as v=9.The enhancement of the vibrational excitation of the reactants made the degree of the forward scattering of the product increased.Then,with the same collision energy,we studied the effect of the rotational quantum number on dynamics.It was found that the rotational excitation of the reactants had little effect on the integral cross section for the reaction,but had the strong impact on the polarization and orientation of the rotational angular momentum of the product.With the increase of rotational excitation,the polarization degree and the orientation effect of the rotational angular momentum of the H₂ molecule reduce.Finally,we considered the effect of the isotopic substitution of the target atom and the target molecule on the dynamics of the reaction.It was found that the degree of the former scattering of product H₂ was weakened when the target molecule H was replaced by D,while the polarization degree and orientation degree of the product rotational angular momentum j’ were little affected.When the attack atom H was replaced by D,the former and the backward scattering degree of product were enhanced,and the polarization degree and orientation degree of the product rotational angular momentum j’ were decreased.