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arXiv 1611.04585physics.atom-phastro-ph.SR
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Si III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 III

K M Aggarwal

摘要:

报道了具有天体物理重要性的类镁离子Si~III的四种类型跃迁(E1、E2、M1和M2)的能级和辐射率(A值),其发射线已在多种等离子体中观察到。对于计算,已采用众所周知的和广泛使用的GRASP代码,并列出了3 $\ell3\ell'$和3 $\ell$ 4 $\ell$配置的141个能级之间的跃迁的结果。只有最低的58个能级的实验能量是可用的,但与理论结果没有重大差异。同样,A值和寿命显示出令人满意的协议与其他可用的结果,特别是对于强E1跃迁。碰撞强度也计算,与DARC代码,并列出了共振跃迁在很宽的能量范围内,高达30-Ryd。文献中没有类似的结果可供比较。然而,比较与更重要的参数,有效碰撞强度($Υ$),最近的$R$矩阵的结果是可用于广泛的过渡,并在很大的温度范围内。为了确定$Υ$,共振已被解决在一个狭窄的能量网格,虽然这些没有被观察到是重要的,因为其他离子。不幸的是,在大约一半的转变中注意到$Υ$值的较大差异。这种差异随着温度的升高而增大,并且随着上能级J的增大而恶化。在大多数情况下,早期的结果被高估了(几乎)两个数量级,这个结论与早期观察到的Be离子一致。

英文摘要:

Energy levels and radiative rates (A-values) for four types of transitions (E1, E2, M1, and M2) are reported for an astrophysically important Mg-like ion Si~III, whose emission lines have been observed in a variety of plasmas. For the calculations, well-known and widely-used GRASP code has been adopted, and results are listed for transitions among the 141 levels of the 3$\ell3\ell'$ and 3$\ell$4$\ell$ configurations. Experimental energies are available for only the lowest 58 levels but there is no major discrepancy with theoretical results. Similarly, the A-values and lifetimes show a satisfactory agreement with other available results, particularly for strong E1 transitions. Collision strengths are also calculated, with the DARC code, and listed for resonance transitions over a wide energy range, up to 30~Ryd. No similar results are available in the literature for comparisons. However, comparisons are made with the more important parameter, effective collision strength ($Υ$), for which recent $R$-matrix results are available for a wide range of transitions, and over a large range of temperatures. To determine $Υ$, resonances have been resolved in a narrow energy mesh, although these are not observed to be as important as for other ions. Unfortunately, large discrepancies in $Υ$ values are noted for about half the transitions. The differences increase with increasing temperature and worsen as the upper level J increases. In most cases the earlier results are overestimated, by up to (almost) two orders of magnitude, and this conclusion is consistent with the one observed earlier for Be-like ions.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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