【作者】 王国利；

【导师】 周效信；

【作者基本信息】 西北师范大学 ， 原子与分子物理， 2009， 博士

【摘要】 原子和离子的光电离是光与原子相互作用的主要过程之一。研究原子的光电离过程有助于了解原子中的电子关联和相对论效应。光电离截面以及与之相关的一些物理量（共振位置、宽度、振子强度）在天体物理、等离子体物理、大气科学、辐射物理和化学等学科都具有很强的应用需求。本文利用R-矩阵方法对部分原子和离子的价壳层、内壳层光电离过程进行了较详细的研究。具体来说,本文的主要内容如下:1.由于已有的一些关于类Be和类B离子的光电离截面的理论计算结果与最新的实验结果之间存在较大的差异,本文使用R-矩阵方法在LS耦合下计算了类Be的N³⁺和O⁴⁺离子的基态1s²2s^{2 1}S和激发态1s²2s2p ³P°的电离阈值附近的光电离截面。通过分光电离截面,指出实验结果对个别共振峰的辨认是错误的。通过光电离截面我们得到了里德堡系列2pnp³D、³S、2pnd ¹P°的共振能量。同时我们使用R-矩阵方法对类B的N²⁺、O³⁺和F⁴⁺离子基态2s²2p ²P°和激发态2s2p^{2 4}P的价壳层光电离过程进行了较详细的研究。在我们计算的激发态光电离截面中发现了2p²（³P）np ⁴D°、⁴P°里德堡共振系列。对个别实验中未能辨认的共振给出了正确的标记。本文计算的结果和已有的理论和实验结果进行了比较。相对已有的理论计算结果而言,本文的计算结果有了一定的改进,本文计算得到的共振结构和位置与最新的实验符合得更好。2.使用R-矩阵方法计算了Be原子基态1s²2s^{2 1}S的光电离截面。通过光电离截面得到了K壳层跃迁1s（2s2p ¹P3s）¹P°、1s（2s2p ³Pns）¹P°（n=5-12）和1s（2s2p ³Pnd）¹P°（n=5,6）系列的共振能量,本文的结果和最新的实验结果符合得很好。3.使用R-矩阵方法对C⁺离子基态1s²2s²2p ²P°和激发态1s²2s2p^{2 4}P、²D、²P、²S、1s²2p³⁴S°的K壳层光电离进行了28-态的密耦计算。由光电离截面所展现的共振结构,我们得到了C⁺离子1s-2p跃迁的共振能量、宽度和振子强度等参数。计算得到的共振能量与已有的其它实验和理论结果符合得很好,但是共振宽度与其它结果仍然存在一些差别。这些数据对分析等离子体光谱会有所帮助。4.分别利用非相对论和相对论R-矩阵方法详细计算了Mg原子基态2p⁶3s^{2 1}S₀的光电离截面。目前的结果表明,即使对于中Z素,相对论效应（主要为自旋-轨道相互作用）也是非常重要的。与非相对论计算结果相比,相对论效应（能级分裂）导致光电离截面中展示了更多的共振结构。在我们的计算中发现了5个自电离里德堡系列:3pns ¹P、3pnd ¹P、3pns³P、3pnd ³D、3pnd ³P,其中3pnd ³P系列为第一次研究发现。通过拟合共振峰我们也得到了这些共振的位置和宽度,结果与最新的实验结果符合得非常好。更多还原

【Abstract】 Photoionization is the one of the main process when photon interacts with atoms and ions. Studying photoionization of atomic systems provides the opportunity to investigate the dynamic interplay among many-body electron-electron correlations and relativistic effects. The data on the cross sections or related quantities for photoionization processes are eagerly needed in many fields of application such as astrophysics, atmospheric science, plasma science, radiation physics and chemistry, etc.The photoionization of atoms and ions are studied theoretically by using the R-matrix method in this thesis. The following is the main contents of the present thesis:1. There exist notable discrepancies with regard to the resonance structures when compared previous theoretical calculations with recent absolute experimental measurements for some Be-like and B-like ions. The photoionization cross section of Be-like ions N³⁺ and O⁴⁺ from the ground state 2s^{2 1}S and excited state 2s2p ³P°near the thresholds range are calculated using the R-matrix method. The resonance energies of 2pnp ³D,³S and 2pnd ¹P°Rydberg states are determined by analyzing the resonance structures of the photoionization cross sections. Detailed calculations are also performed on the photoionizations of the ground state 2s²2p ²P°and excited state 2s2p^{2 4}P of B-like ions N²⁺, O³⁺ and F⁴⁺. In photoionization cross sections of B-like ions we find resonances 2p²（³P）np ⁴D°,⁴P°for the first time. Our results show a good improvement in comparison with previous theoretical results.2. 25-state close-coupling calculations using the R-matrix method are carried out for the photoionization cross section of the ground state of Be atoms. The resonance energies of series 1s（2s2p ¹P3s）¹P°, 1s（2s2p ³Pns） ¹P°（n=5-I2） and 1s（2s2p ³Pnd）¹P°（n=5,6） are obtained from the photoionization cross sections. Present values are higher no more than 0.15 eV when compared with experimental results.3. Detailed 28-state close-coupling calculations based on an R-matrix formalism have been carried out to investigate the K-shell photoionization cross sections from the states 1s²s²2p ²P°, 1s²2s2p^{2 4}P,²D,²P,²S and 1s²2p^{3 4}S°of B-like CⅡions. Emphasis is laid on analyzing the 1s—2p resonances and on obtaining the resonance energies, widths of the core-excited states and the oscillator strengths of the 1s—2p transitions. The calculated resonance energies, autoionization widths are compared with existing experimental and theoretical results. Rather good agreement is found between our results and other experimental and theoretical results, but for autoionization widths there remain some differences. The present numerical values may help the analysis of astrophysical and laboratory plasmas. 4. The photoionization cross section of the ground level （3s^{2 1}S₀） of atomic magnesium has been studied theoretically in the energy region between the Mg⁺（3s） and Mg⁺（3p） threshold using both the relativistic and nonrelativistic R-matrix method. Our results show that even for the intermediate-Z elements, the relativistic effects （mainly the spinorbit interactions） should not be neglected. The relativistic effects result in more extensive resonance structures due to many more coupled channels and different positions of resonances. The positions and widths of resonances have also been obtained and compared with a recent experiment. Excellent agreement is shown between our relativistic calculations and experimental measurements. In the present calculations, five Rydberg series of doubly excited states have been exhibited, i.e., 3pns ¹P, 3pnd ¹P, 3pns ³P, 3pnd ³D and 3pnd ³P, where the 3pnd ³P are found as the new fifth series.更多还原