基于新CH2(X-3A″)势能面的C(3P)+H2(X1∑g^+)→H(2S)+CH(2Π)反应量子波包动力学

Wave packet quantum dynamics of C(3P)+H2(X1∑g^+)→H(2S)+CH(2Π)reaction based on new CH2(X-3A″)surface

基于一个最新的CH2(X-3A″)势能面,运用切比雪夫波包方法对初始态为(v=0,j=0)的C(3P)+H2(X1∑g^+)→H(2S)+CH(2Π)反应体系在1.0-2.0 eV的碰撞能量范围内进行了动力学研究.通过对角动量量子数J=60以下的所有分波进行计算,得到了反应几率、积分散射截面和速率常数.计算中用到了耦合态近似方法和考虑科里奥利耦合效应的精确量子方法.通过对比发现,随着角动量量子数以及能量的增加,科里奥利耦合效应的影响越发显著,因而对于该反应体系,科里奥利耦合效应不可忽略.本文计算所得的积分散射截面和速率常数尚无实验数据可以比较,对该反应的后续研究有一定的参考价值.

The C(3P)+H2→CH+H reaction in a collision energy range of 1.0–2.0 e V with the initial stateν=0,j=0is investigated based on the new potential energy surface(PES)by using the Chebyshev wave packet method.All partial wave contributions up to J=60 are calculated explicitly by the coupled state(CS)approximation method and the Coriolis coupling(CC)effect.Dynamic properties such as reaction probabilities,integral cross sections,and state specific rate constants are calculated.The calculated probabilities and integral reaction cross sections display an increasing trend with the increase of the collision energy and an oscillatory structure due to the CH2 well on the reaction path.The thermal rate constants of the endoergic reaction with a temperature ranging from 1000 K to 2000 K are obtained also.The calculated rate constants increase in the entire temperature range,showing a sharp T dependence in a range of 1400–2000 K.The rate constants are sensitive to the temperature due to the high threshold of the title reaction.In addition,the results of the exact calculations including CC effect are compared with those from the CS approximation.For smaller J,the CS probabilities are larger than the CC results,while for larger J,they are smaller than the CC ones.For reaction cross sections and rate constants,the CS results and the CC ones are in good agreement with each other at lower energy.However,they turn different at higher energy.The comparison between the CC and CS results indicates that neglecting the Coriolis coupling leads the cross sections and the rate constants to be underestimated due to the formation of a CH2 complex supported by stationary point of CH2(X-3A″)PES.It is suggested that the CH2 complex plays an important role in the process of the title reaction.However,it seems to overestimate the CS and CC rate constants because the barrier recrossing is neglected.Unfortunately,the results obtained in the present work have no corresponding theoretical or experimental data to be compared with,therefore these results provide simply a certain reference significance to the follow-up study of the title reaction.