Resonance enhanced electron impact excitation of Cu-like gadolinium

Abstract: Employing the independent processes and isolated resonances approximation using distorted-waves (IPIRDW), we perform a large calculation and a detail investigation on resonance enhanced electron impact excitation (EIE) among the 27 singly excited levels from n ≤ 6 configurations of Cu-like gadolinium (Gd, Z = 64). We take into account the RE contributions from both the relevant Zn-like doubly excited series [Ne]3l¹⁸n′l′n′′l′′ with n′ = 4–7, and the series [Ne]3l¹⁷4l4l′n′′l′′. Results show that the RE contributions are significant and enhance effective collision strengths (Υ) of certain excitations by even up to an order of magnitude at low temperature (10^5.8 K), and still important at relative high temperature (10^6.8 K), where the fraction abundance of Gd XXXVI is expected at peak. We expect present resonance enhanced EIE results among the 27 levels, which is the first results with the RE contributions from n = 3 → 4 core excitation for Cu-like isoelectronic sequence, are more accurate due to our consideration of RE contributions for this ion for the first time. Graphical abstract: [Figure not available: see fulltext.].