Electron impact excitation of Be-like ions: a comparison of darc and icft results
Electron impact excitation of Be-like ions: a comparison of darc and icft results
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DOI：
10.1093/mnras/stu2727
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发表时间：
2015-01
影响因子：
4.8
通讯作者：
K. Aggarwal;F. Keenan
中科院分区：
文献类型：
--
作者：
K. Aggarwal;F. Keenan
Be 类离子的发射线经常在天体物理等离子体中观察到，其中许多对于密度和温度诊断很有用。然而，可靠的等离子体建模需要准确的能级、辐射率（A 值）和有效电子激发碰撞强度（$\Upsilon$）原子数据。一般来说，以高精度计算能量水平和 A 值是相当简单的。相比之下，计算 $\Upsilon$ 需要相当大的努力，因此并不总是能够评估可用数据的准确性。最近，针对一系列 Be 类离子出现了两种独立的计算（采用 $R$ 矩阵方法）但采用不同的方法（DARC 和 ICFT）。因此，在这项工作中，我们比较了两组 $\Upsilon$，突出显示了大量转换的巨大差异，并提出了可能的原因。
Emission lines of Be-like ions are frequently observed in astrophysical plasmas, and many are useful for density and temperature diagnostics. However, accurate atomic data for energy levels, radiative rates (A-values) and effective electron excitation collision strengths ($\Upsilon$) are required for reliable plasma modelling. In general it is reasonably straightforward to calculate energy levels and A- values to a high level of accuracy. By contrast, considerable effort is required to calculate $\Upsilon$, and hence it is not always possible to assess the accuracy of available data. Recently, two independent calculations (adopting the $R$-matrix method) but with different approaches (DARC and ICFT) have appeared for a range of Be-like ions. Therefore, in this work we compare the two sets of $\Upsilon$, highlight the large discrepancies for a significant number of transitions and suggest possible reasons for these.