HONO分子的多体项展式势能函数和H+NO_2反应动力学的研究

MANY-BODY EXPANSION OF THE POTENTIAL ENERGY FUNCTION FOR HONO AND DYNAMICAL STUDY FOR THE REACTION OF H+NO_2

导出了基态HONO分子的分析势能函数,该函数预计反应H+NO_2→OH+NO的最小能量途径上具有一个势阵,并在入口和出口通道上不存在固有势垒。采用QCT方法计算了该反应的动力学过程,结果表明,它是一个“复合“碰撞反应,中间络合物的寿命约为1.0×10^(-12)秒,并且是一个无阈能的反应,及资用能主要分配在产物分子的振动能和转动能。求得宏观速度常数(298K)为1.748×10^(-10)cm^3·molecule^(-1)·sec^(-1),与实验测定值1.41±0.26×10^(-10)吻合很好。

An explicit function has been derived for the potential-energy surface of the ground state of HONO with the six interatomic distances as variables.This surface predicts that there exists a well on the reaction path from the reactant H+NO2 to the product HO + NO without the barrier in the entrance or exit channel. The surface has been used to calculate classical trajectories for the reaction H(2S) + NO2(X2A1)→OH(X2п) + NO(X2п).The angular distribution is nearly symmetric, and the reactive trajectories show a short-lived HONO complex with a lifetime of roughly 1.0×10~12sec. The cross section decreases with increasing the translational energy, implying this reaction with no threshold energy,From the 298K results an approximate rate constant has been obtained of 1.748× 10-10cm3. molecule-1, sec-1, which is in good agreement with the experimental value of 1.41 ±0.26×10-10. In addition, the rate constant is obviously dependent on the temperature. Only 23.2 per cent of the total energy released appears in translational energy, 22.8 per cent vibrational and 19.3 per cent rotational for HO, and 21.6 per cent vibrational and 12.5 per cent rotational for NO.The calculations yield the following relative vibrational populations: for HO, N0:N1:N2 :N3=2.28: 1.0; 0.36; 0.04; for NO, N0:N1:N2:N3:N4:N5:N6 = 1.41; 1.0; 0.65; 0.33; 0.17; 0.07; 0.04.