Partial Photoionization Cross Sections of Chromium from the Ground and Excited States
Partial Photoionization Cross Sections of Chromium from the Ground and Excited States
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DOI：
10.3390/atoms8030051
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发表时间：
2020-08
期刊：
影响因子：
1.8
通讯作者：
O. Zatsarinny;S. Tayal
中科院分区：
文献类型：
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作者：
O. Zatsarinny;S. Tayal
铁峰元素的部分和全部光电离截面对确定晚型恒星和星云天体的丰度具有重要意义。我们研究了中性铬从基态和激发态在6.77 eV至30 eV的低能区的光电离。用多组态Hartree-Fock方法精确地描述了Cr I的初始束缚态和Cr II的最终剩余离子态，以及可调的组态展开和项相关的非正交轨道。用b样条r矩阵法计算了光电离截面。Cr II 3d44s、3d34s2、3d5、3d44p和3d34s4p主构型的194 LS终离子态已包含在紧耦合展开中。这些构型的所有项的包含对近阈值共振结构和非共振背景截面有显著的影响。将Cr I的接地态3d54sa7S和激发态3d54sa5S、3d44s2a5D、3d54pz5P和3d44s4py5P的总光离截面与其他可用的r矩阵计算方法进行了比较，以估计光离截面可能存在的不确定性。我们分析了剩余离子在不同状态下的部分光离截面，以确定重要的散射通道，并注意到三维电子电离通道在高能量下占主导地位。
Partial and total photoionization cross sections of iron-peak elements are important for the determination of abundances in late-type stars and nebular objects. We have investigated photoionization of neutral chromium from the ground and excited states in the low energy region from the first ionization threshold at 6.77 eV to 30 eV. Accurate descriptions of the initial bound states of Cr I and the final residual Cr II ionic states have been obtained in the multiconfiguration Hartree-Fock method together with adjustable configuration expansions and term-dependent non-orthogonal orbitals. The B-spline R-matrix method has been used for the calculation of photoionization cross sections. The 194 LS final ionic states of Cr II 3d44s, 3d34s2, 3d5, 3d44p, and 3d34s4p principal configurations have been included in the close-coupling expansion. The inclusion of all terms of these configurations has significant impact on the near-threshold resonance structures as well as on the nonresonant background cross sections. Total photoionization cross sections from the ground 3d54sa7S and excited 3d54sa5S, 3d44s2a5D, 3d54pz5P, and 3d44s4py5P states of Cr I have been compared with other available R-matrix calculation to estimate the likely uncertainties in photoionization cross sections. We analyzed the partial photoionization cross sections for leaving the residual ion in various states to identify the important scattering channels, and noted that 3d electron ionization channel becomes dominant at higher energies.