氖原子光电子角分布的理论计算

Theoretical calculation of the photoelectron angular distribution of neon

本文利用密度矩阵理论和Racah代数推导出了光电子角分布的一般计算公式,并在多组态Dirac-Fock方法基础上发展了计算原子光电离过程中产生的光电子角分布的相对论程序,利用该程序对氖原子2s和2p光电子角分布的偶极和非偶极参数进行了具体计算,所得结果与已有文献具有很好的一致性.在此基础上,本文讨论了光子与电子相互作用多级展开中的非偶极项以及入射光的极化性质对光电子角分布的影响.

The general formula of the angular distribution of photoelectron is derived by using the density matrix theory and Racah algebra method. For comparing with the experimental data, the general formula in this paper is matched to the parametric formula and the non-dipole parameters of the photoelectron angular distribution associated with the terms of the second order for both unpolarized and polarized incident light are given explicitly. From the formula of these parameters we can see that the contribution to the non-dipole parameter is from the interference between dipole amplitude and multipole amplitude. And then, the relativistic calculation program for photoelectron angular distribution is further developed with the help of the program packages GRASP2 K and RATIP which are based on the multi-configuration Dirac-Fock method. By using this program, the dipole and non-dipole angular-distribution parameters for neon 2s and 2p photoelectrons are calculated concretely. The good agreement between the results of this paper and the available theoretical data is obtained in a 50–5000 e V photoelectron-energy range studied. On this basis, the angular photoelectron distributions for neon 2s and 2p are calculated with and without considering the second non-dipole terms at the photoelectron energy E = 600 e V and E = 5000 e V, respectively. Special attention is paid to the effects of the polarization property of incident light and the non-dipole terms of photo-electron interaction on the angular distribution of photoelectrons. The results show that 1） the dipole and non-dipole parameters of the photoelectron angular distribution are sensitive to the ionized electron orbital, it can bring out considerable diversities among the photoelectron angular distributions of the different shells; 2） non-dipole effects make the photoelectron forward distribution in the direction of incident light, the polarization property of incident light will strengthen the asymmetric distribution of photoelectrons.