【作者】 韩小英；

【导师】 李家明；

【作者基本信息】 清华大学 ， 物理学， 2007， 博士

【摘要】 原子(离子)的光电离截面以及带电粒子(特别是电子)与原子(离子)的弹性和非弹性碰撞散射截面数据是天体物理、空间和大气物理、等离子体物理等领域研究中必不可少的物理参数。我们用最新发展的Breit-Pauli R-矩阵程序计算了基态Na原子的光电离截面。我们计算的靶态能级以及第一电离阈值都和实验值符合在1%以内。在光子能量比较低的区域(5?13 eV),我们计算的光电离截面以及吸收窗口位置是目前和实验值符合最好的计算结果。在吸收窗口以上,实验测量结果中有个奇异的隆起,这是理论和实验研究之间一个长期无法解释的矛盾。有趣地是我们发现Na+2分子离子的光电离截面(即光解离截面)中也存在一个吸收窗口,这个吸收窗口为这个长期存在的矛盾提供了一个合理的解释。此外,用上面经过检验的靶态和单轨道波函数基计算了激发态Na原子的光电离截面。我们的计算结果和最新的实验结果符合很好。因此,这说明Breit-Pauli近似下的R-矩阵方法以及相应的程序能同时处理好中Z元素原子光电离过程中的电子关联作用和相对论效应(主要是自旋-轨道相互作用)。我们用分波法计算了Na原子与低能电子的碰撞散射截面,研究了分波散射截面随激发能以及轨道角动量变化的性质。此外,在一阶波恩近似下,我们用最新发展的R-矩阵程序计算了He原子与高能电子碰撞的广义振子强度以及广义振子强度密度曲面,我们的计算结果和最新的实验结果符合很好。进一步,我们提出了一个计算中能电子碰撞散射截面的方案。经过最新的实验严谨检验的R-矩阵方法以及相应的程序预期能为天体物理、空间和大气物理、等离子体物理、聚变物理、激光物理等领域的研究提供大量精密的原子物理参数。更多还原

【Abstract】 Photoabsorption (including the photoexcitation and photoionization) and electroncollision scattering cross sections are the indispensable physical parameters in laserphysics, radiation physics, plasma physics, atmospheric physics and astrophysics.Using our modified Breit-Pauli R-matrix code, the photoionization cross sectionsof ground Na are calculated. Our calculated cross sections and minimum position in thelow photon energy range (5?13 eV) are in excellent agreement with the experimentalresults. In the high energy range, there is an abnormal bump in the experimental mea-surements, which is a long-standing experimental puzzle. It is interesting to note thatthere is also an absorption window in the photoabsorption (i.e. photodissociation) crosssections of Na2+ . Such absorption window provides an answer to the puzzle. Based onthe same target and orbital bases, we calculated the photoionization cross sections ofexcited Na. Our calculated branching ratios of the J-resolved partial cross sectionsare in good agreement with the recent measurements within the experimental uncer-tainties. The excellent agreement between our theoretical results and the experimentalresults demonstrates that both the electron correlations and the relativistic effects canbe treated adequately on equal footing by the theoretical method and modified codes.Using the partial wave method we calculated the scattering cross sections of Naimpacted by the low-energy electron. We studied the features of the partial wave scat-tering amplitudes. Using the modified R-matrix code we calculated the GOSs of He-lium impacted by the high-energy electron within the First Born Approximation. TheGOSD surfaces of 1S, 1P and 1D channels are calculated and tested stringently by therecent experiments. In addition to the low- and high-energy electron impact excitationcross sections, a scheme to calculate the cross sections in the entire incident energyrange is discussed.更多还原