Electron-impact excitation of Cr II A theoretical calculation of collision and effective collision strengths for forbidden transitions
Electron-impact excitation of Cr II A theoretical calculation of collision and effective collision strengths for forbidden transitions
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Cr II 的电子碰撞激发禁戒跃迁碰撞和有效碰撞强度的理论计算
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
P. Norrington
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作者：
I. R. Wasson;C. Ramsbottom;P. Norrington
上下文在各种各样的天体物理光谱中观察到Cr II的吸收或发射谱线，迫切需要准确的原子数据来解释这些谱线。这些数据中的许多是不可能通过实验测量的，并且完整的理论处理是可以获得这些数据的唯一手段。目标。在本文中，我们提出的碰撞强度和有效碰撞强度的电子碰撞激发铬二禁戒跃迁之间的最低的说谎74精细结构的水平。计算了18个具有天体物理意义的电子温度（2000- 100000 K）的有效碰撞强度。方法. R-矩阵包，RMATRX II，最近已被扩展到允许列入相对论效应的并行套件，已被用于在目前的工作中计算的碰撞强度和有效的碰撞强度为electronimpact激发铬二。在这篇文章中，我们集中在最低的74个jj精细结构能级与配置3d 5和3d 4 4s之间的低位禁戒线，虽然原子数据已被评估的280个jj能级之间的配置3d 5，3d 4 4s和3d 4 4p的所有39 060跃迁。这项工作构成了有史以来最大的评估，涉及1932耦合通道的离子。结果碰撞和有效碰撞强度的所有过渡之间的最低74 Jπ态的Cr ii和Bautista等人（2009）的工作进行了比较。虽然有效的碰撞强度同意一些过渡，其他人存在显着的差异。我们相信，目前的原子数据是电子碰撞激发Cr Ⅱ的最准确、最精密、最完整的数据集，我们将把它们推荐给天体物理学家和等离子体物理学家的应用工作。我们期望，为重要的低位禁戒线提供的有效碰撞强度精确到15%以内。
Context. Absorption or emission lines of Cr ii are observed in a wide variety of astrophysical spectra and accurate atomic data are urgently needed to interpret these lines. Many of these data are impossible to measure experimentally and a full theoretical treatment is the only means by which these data can be obtained. Aims. In this paper, we present collision strengths and effective collision strengths for electron-impact excitation of Cr ii for forbidden transitions among the lowest-lying 74 fine-structure levels. Effective collision strengths have been computed for 18 individual electron temperatures of astrophysical importance, ranging from 2000–100 000 K. Methods. The parallel suite of R-matrix packages, RMATRX II, which has recently been extended to allow for the inclusion of relativistic effects, has been used in the present work to compute the collision strengths and effective collision strengths for electronimpact excitation of Cr ii. We concentrate in this publication on low-lying forbidden lines among the lowest 74 jj fine-structure levels with configurations 3d 5 and 3d 4 4s, although atomic data has been evaluated for all 39 060 transitions among the 280 jj levels of configurations 3d 5 ,3 d 4 4s and 3d 4 4p. This work constitutes the largest evaluation ever performed for this ion involving 1932 coupled channels. Results. Collision and effective collision strengths are presented for all transitions among the lowest 74 Jπ states of Cr ii and comparisons made with the work of Bautista et al. (2009). While the effective collision strengths agree well for some transitions, significant discrepancies exist for others. We believe that the present atomic data represents the most accurate, most sophisticated and most complete data set for electron-impact excitation of Cr ii and we would recommend them to astrophysicists and plasma physicists in their application work. We would expect that the effective collision strengths presented for the important low-lying forbidden lines are accurate to within 15%.