【作者】 桑萃萃；

【导师】 董晨钟；

【作者基本信息】 西北师范大学 ， 原子与分子物理， 2008， 硕士

【摘要】 光电离是光与原子或离子作用的主要过程之一,是辐射复合的逆过程。对光电离过程的研究在天体物理、X射线激光、高温等离子体以及热核聚变等的研究中都有广泛应用。在本论文中,对光电离截面随光子能量的变化规律、光电离末态的Auger退激发过程以及光电离的逆过程—辐射复合做了初步的研究。以锂原子为例,研究了光电离截面随光子能量的变化规律、弛豫效应对光电离截面的影响以及主光电离截面和振激光电离截面随价电子态的变化规律。结果表明:随着光子能量的增大,光电离截面普遍减小。在原子内壳层电子的光电离过程中,弛豫效应较强,而在外壳层电子的光电离过程中,弛豫效应较弱。对应于不同态的内壳层光电离过程,弛豫效应的影响也不同:对激发态的影响比对基态的影响大,对高激发态的影响比对低激发态的影响大。内壳层电子的主光电离截面和振激光电离截面随着初态中价电子态的升高会发生剧烈的变化,尤其是在电离域附近,但是没有呈现出明显的规律。以碱金属元素K和Rb以及稀有气体元素Ne和Ar为例,研究了内壳层光电离末态的Auger退激发过程。首先计算了处于基态和亚稳态的K和Rb的光电子谱和Auger谱,与最新的实验做了比较,符合很好。其次计算了处于基态和亚稳态的Ne和Ar的光电子谱和Auger电子谱并分析了其结构。通过对碱金属元素和稀有气体元素的光电子谱和Auger电子谱的分析可知:从基态光电离内壳层电子的几率大于从亚稳态光电离内壳层电子的几率;“共轭”光电离过程对Auger谱的影响相比主光电离和振激光电离过程对Auger谱的影响小一到两个数量级。以高离化态金离子(类镍Au51+、类铜Au50+和类锌Au49+离子)为例,研究了光电离的逆过程—辐射复合及其辐射退激发过程。其中,辐射复合谱与已有实验结果符合很好。研究结果表明:对于类镍Au51+、类铜Au50+和类锌Au49+离子而言,将一个自由电子俘获到n = 4壳层的几率最大。在辐射复合过程之后,处在n = 4壳层的俘获电子的辐射退激发谱线最强,并且体现了整个辐射退激发级联谱的主要特征。更多还原

【Abstract】 Photoionization (PI) is the main process when photon interacts with atoms and ions. Studies on PI are important in astrophysics, X-ray, high temperature plasmas, etc. In the present work, we studied the regulation of the PI cross sections on photon energy, auger processes of PI final states and the inverse process of PI—radiative recombination (RR).Take lithium as an example, we studied the regulation of the PI cross sections depend on photon energy, and the affect of relaxation effect on PI and, furthermore, the regulation of the main and shake-up processes depend on valence electron orbitals. It is found that along with increasing photon energy, cross sections of PI decrease. The relaxation effect plays an important role in the inner-shell PI processes, while in the outer-shell PI processes it can be ignored. The effect of relaxation on inner-shell PI processes from different states is not the same: It is more important for the excited states than the ground state, and for the higher excited states than the lower excited states. Furthermore, main and shake-up processes depend on valance electron orbitals strongly, but without any obvious regulations.Take the alkali metals potassium and rubidium as well as the rare gases neon and argon as an example, we studied the auger decay processes of the final states of inner-shell PI. Firstly, we calculated the photoelectron spectrum and auger spectrum of potassium and rubidium at both ground states and metastable states. Good agreements are found between our results and the latest experiments. Secondly, we calculated the photoelectron spectrum and auger spectrum of neon and argon at both ground states and metastable states, and analyzed the structures in detail. We could conclude from the calculated spectrums that the probability of an inner-shell electron to be photoionized is bigger from the ground states than from the metastable states; The effect of the so called‘conjugate’PI processes on auger spectrum is one to two order smaller than the main and shake-up PI processes.Take highly charged (from Ni-like to Cu-like) gold ions as an example, we studied the inverse process of PI—RR and the accompanying radiative decay processes. Good agreements are found between the calculated RR spectrum and the latest experiment in EBIT. It is found that for the highly charged Au ions (Ni–like Au51+, Cu–like Au50+ and Zn–like Au49+), the probability for capturing a free electron into n = 4 subshell is the largest. The main character of the RDC spectra depend on the lines from the captured electron decaying within n = 4 subshell.更多还原