Collisions of highly charged ions with relativistic effects by electron impact in plasmas

等离子体中离子的发射和离子的电子碰撞激发截面可以用来获得等离子体诊断的电子温度和密度。本项目的目的是研究相对论效应对电子碰撞离子激发截面的影响。我们采用了三种R矩阵方法，即非相对论R矩阵（RMAT）、Breit-Pauri近似下的半相对论R矩阵（BPRMAT）和Dirac近似下的全相对论R矩阵（DRMAT），所得理论结果可作为碰撞辐射模型的输入数据用于等离子体诊断。研究结果如下：1.利用DRMAT近似、紧耦合近似和库仑玻恩近似计算了类氢离子n=2精细结构能级间的电子碰撞跃迁。发现电子交换效应对光禁戒跃迁截面有很大的贡献.用DRMAT、BPRMAT和RMAT计算了类He离子（Z=16-26）的电子碰撞激发截面和速率系数。在计算中包括最低的45个目标水平，以获得基态到激发态的速率系数，其中n=2、3和4。结果表明，n=5能级的耦合效应和共振效应对n=4能级跃迁的速率系数有重要影响.利用RMAT和BPRMAT计算了类锂离子、类镁离子和钙离子的激发截面和Stokes参数。结果表明，本文的计算结果与实验符合得很好，为等离子体诊断提供了可靠的依据。

Emissions from ion in plasmas and excitation cross sections of the ion by electron impact can be used to obtain electron temperature and density for plasma diagnostics. The aim of this project is to study relativistic effects for excitation cross sections of ions by electron impact. We used three kinds of R-matrix methods viz. non-relativistic R-matrix (RMAT), semi-relativistic R-matrix (BPRMAT) with the Breit-Pauri approximation and full relativistic R-matrix (DRMAT) with the Dirac approximation.Present theoretical results are available to use as input data on a collisional radiative model for plasma diagnostics. The results are summarized as follows.1. The electron-impact transitions between the n=2 fine-structure levels of hydrogenic ions were calculated using the DRMAT, the close-coupling and the Coulomb-Born approximations. It was found that the electron-exchange effect was a considerable contribution to the cross-section of optically forbidden transitions.2. Cross sections and rate coefficients for electron-impact excitation of He-like ions (Z=16-26) were calculated by use of the DRMAT, the BPRMAT and the RMAT. The lowest 45 target levels were included in the calculation to obtain the rate coefficients for the ground state to the excited states with n=2, 3 and 4. It was verified that the effects of coupling and resonances from n=5 levels play an important role in rate coefficients for the transitions to the n=4 levels.3. Excitation cross sections and Stokes parameters of Li-like and Mg-like ions, and Ca were obtained by using the RMAT and BPRMAT. It was shown that present results were in excellent agreement with the experiments and reliable for plasma diagnostics.