中文摘要：

采用相对论多组态Dirac-Fock理论,计算了Na原子及类Na离子Fe15＋基态的光电离截面.对Na原子,考虑相对论效应与弛豫效应,本文计算结果与前人计算结果和实验测量结果一致性较好.对Fe15＋离子的最外价电子,相对论效应对其光电离过程产生主要影响,而轨道弛豫效应则可忽略不计;对中性Na原子则情况完全不同：轨道弛豫效应的影响非常显著,但其光电离截面对相对论效应仅有非常微弱的依赖.

英文摘要：

Calculations of photoionization cross sections for Na atoms and Na-like Fe15＋ ions were carried out in the framework of relativistic multiconfiguration Dirac-Fock method. For Na atoms, comparisons were made with previous theoretical calculations and available experimental measurements and a good or at least reasonable agreement is found if the relativistic and relaxation effects are taken into account. It is shown that, for the outermost valence electrons of medium Fe15＋ ions, the relativistic effects accounts for a prominent part in the photoionization process and orbital relaxation can he negligible; however it is not the same case for neutral Na atoms where the influence of orbital relaxations is significant but cross sections slightly depend on the relativistic effects.