标题： 氦-like 氧的电子碰撞激发，包括辐射阻尼至 n = 4 能级 显示英文标题

标题： Electron impact excitation of helium-like oxygen up to n = 4 levels including radiation damping

摘要： X射线诊断线在类氦离子中主要由基态到n = 2能级的电子碰撞激发，但在高温下n > 2能级也会被激发。 为了更全面地描述原子过程，计算了OVII的碰撞强度，这是首次包括以下所有内容：(i) 相对论精细结构，(ii) 能级达到n = 4，以及(iii) 自电离共振的辐射阻尼。 计算使用Breit-Pauli R矩阵（BPRM）方法，采用31个能级本征函数展开。 碰撞强度中的共振结构在n = 4阈值内被详细描绘。 对于高电荷数的类氦离子，自电离共振的辐射阻尼是已知的重要现象。 我们对此效应进行了详细研究，并发现虽然当系列极限n --> ∞从下方接近时，共振明显受到辐射阻尼，但对有效截面和速率系数的整体影响非常小。 在X射线等离子体诊断中重要的主谱线w、x、y和z的碰撞强度，对应于到基态1s^2 (^1S_0) <-- 1s2p (^1P^o_1)、1s2p (^3P^o_2)、1s2p (^3P^o_1)、1s2s (^3S_1)的4个跃迁，被明确展示。 发现禁戒z线的有效碰撞强度在T < 10^6 K时比以前的值高出多达4倍。 这可能在光致电离天体物理等离子体的诊断中具有重要意义。 对于其他几个跃迁，也发现了与之前工作显著不同的结果。 这项工作是Iron Project-RmaX网络的一部分。 显示英文摘要

摘要： The primary X-ray diagnostic lines in He-like ions are mainly excited by electron impact from the ground level to the n = 2 levels, but at high temperatures n > 2 levels are also excited. In order to describe the atomic processes more completely collision strengths are computed for OVII including for the first time all of the following: (i) relativistic fine structure, (ii) levels up to the n = 4, and (iii) radiation damping of autoionizing resonances. The calculations are carried out using the Breit-Pauli R-matrix (BPRM) method with a 31-level eigenfunction expansion. Resonance structures in collision strengths are delineated in detail up to the n = 4 thresholds. For highly charged He-like ions radiation damping of autoionizing resonances is known to be significant. We investigate this effect in detail and find that while resonances are discernibly damped radiatively as the series limit n --> infty is approached from below, the overall effect on effective cross sections and rate coefficients is found to be very small. Collision strengths for the principal lines important in X-ray plasma diagnostics, w,x,y and z, corresponding to the 4 transitions to the ground level 1s^2 (^1S_0) <-- 1s2p (^1P^o_1), 1s2p (^3P^o_2), 1s2p (^3P^o_1), 1s2s (^3S_1), are explicitly shown. It is found that the effective collision strength of the forbidden z-line is up to a factor of 4 higher at T < 10^6 K than previous values. This is likely to be of considerable importance in the diagnostics of photoionized astrophysical plasmas. Significant differences are also found with previous works for several other transitions. This work is carried out as part of the Iron Project-RmaX Network.