Si II的能级、辐射率和电子碰撞激发率
Energy levels, radiative rates and electron impact excitation rates for transitions in Si II
摘要：
使用{ \sc grass}（通用相对论原子结构程序包）计算了Si II的3s $^2$ 3 p、3s 3 p $^2$、3 p $^3$、3s $^2$ 3d、3s 3 p3 d、3s $^2$ 4 $\ell$和3s $^2$ 5 $\ell$组态的最低56个能级的能量。使用灵活原子代码（{ \sc fac}）也进行了类似的计算（最多175个级别）。此外，辐射率计算所有的E1，E2，M1和M2跃迁。与现有的理论和实验能级进行了广泛的比较，目前的结果的准确性被评估为优于0.1 Ryd。类似地，对于大多数（强）跃迁，辐射率（以及随后的寿命）的准确性估计优于20%。电子碰撞激发碰撞强度也计算，狄拉克原子R-矩阵代码（{ \sc darc}），在很宽的能量范围高达13 Ryd。最后，为了确定有效碰撞强度，共振在阈值区域中的精细能量网格中被解决。这些碰撞强度是麦克斯韦速度分布的平均值，并列出了高达10 $^{5.5}$ K的宽温度范围内的结果。我们的数据进行了比较与早期的$R$矩阵计算和差异指出，高达两个因素，几个过渡。虽然仍有改进的余地，我们的碰撞强度和有效碰撞强度的结果的准确性评估为约20%的大多数过渡。
英文摘要：
Energies for the lowest 56 levels, belonging to the 3s$^2$3p, 3s3p$^2$, 3p$^3$, 3s$^2$3d, 3s3p3d, 3s$^2$4$\ell$ and 3s$^2$5$\ell$ configurations of Si II, are calculated using the {\sc grasp} (General-purpose Relativistic Atomic Structure Package) code. Analogous calculations have also been performed (for up to 175 levels) using the Flexible Atomic Code ({\sc fac}). Furthermore, radiative rates are calculated for all E1, E2, M1 and M2 transitions. Extensive comparisons are made with available theoretical and experimental energy levels, and the accuracy of the present results is assessed to be better than 0.1 Ryd. Similarly, the accuracy for radiative rates (and subsequently lifetimes) is estimated to be better than 20% for most of the (strong) transitions. Electron impact excitation collision strengths are also calculated, with the Dirac Atomic R-matrix Code ({\sc darc}), over a wide energy range up to 13 Ryd. Finally, to determine effective collision strengths, resonances are resolved in a fine energy mesh in the thresholds region. These collision strengths are averaged over a Maxwellian velocity distribution and results listed over a wide range of temperatures, up to 10$^{5.5}$ K. Our data are compared with earlier $R$-matrix calculations and differences noted, up to a factor of two, for several transitions. Although scope remains for improvement, the accuracy for our results of collision strengths and effective collision strengths is assessed to be about 20% for a majority of transitions.
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