摘要
从含时微扰的一级波恩近似出发 ,进一步研究了CO(A～e)混合态在以He或HCl为碰撞伴时其跃迁振幅和相位角的时间特性 .计算显示跃迁振幅随时间显现衰减的振荡 .其振荡周期反比于初末态的能量差而衰减时间则决定于碰撞体系的分子间相互作用势能 .对于给定的碰撞参数和碰撞速度 ,CO分子从初始转动态J到末态J′的跃迁可经过许多不同的通道 ,包括CO的不同量子数M和碰撞伴的各种J和M .所以实验的跃迁振幅及其实部和虚部是所有不同通道的平均结果 .当He为碰撞伴时 ,所有的单重态和三重态通道的跃迁振幅矢量都处于复平面的第一象限 ,而当HCl为碰撞伴时 ,则单重态和三重态通道的跃迁振幅矢量分别处在第四和第一象限 ,这就解释了以He为碰撞伴时干涉相位角小于 90°而以HCl为碰撞伴时则大于 90°的实验事实 .
A further study on the temporal behavior of collision-induced transition amplitude and phase angle within CO(A～e) mixed states is carried out based on the first order Born approximation of time dependent perturbation theory for He or HCl as the collision partners. The calculation shows that the transition amplitudes appear some damped oscillation with the period reciprocally proportional to the energy gap between the initial and final states while the damping time is determined by the inter-molecular potential of the collision system. For a given impact parameter and collisional velocity, the transition of CO from an initial rotational state J to the final state J′ may proceed through many channels with different quantum numbers M of CO and different J and M quantum numbers of the collision partner. So the experimental transition amplitudes with its real and imaginary parts are the average of all the possible channels. It is interesting to note that in the case of He as the collision partner, all the transition amplitude vectors for both singlet and triplet channels are located in the 1st quadrant of the complex plane, whereas for HCl as the collision partner the transition vectors of singlet and triplet channels are located respectively in the 4th and 1st quadrants. These results well explain the experimental fact that the interference phase angle is smaller than 90o for He as the collision partner, whereas it is larger than 90o for HCl as the collision partner.
基金
ProjectsupportedbytheNationalNaturalScienceFoundationofChina (2 99730 4 5 )
关键词
碰撞量子干涉效应
干涉相位角
跃迁振幅
Collisional quantum interference effect, Interference phase angle, Transition amplitude
