Atomic data from the IRON Project

XLI. Electron excitation rates among the 3d² fine-structure levels of Ca-like Fe VII

¹ School of Science & Mathematics, Sheffield Hallam University, Sheffield S1 1WB, UK
² Department of Materials Science, Faculty of Engineering, Miyazaki University, Miyazaki 889-21, Japan
³ Department of Applied Mathematics & Theoretical Physics, Queen's University, Belfast BT7 1NN, UK

Received: 30 July 1999
Accepted: 22 October 1999

Abstract

Electron excitation collision strengths of 3d² fine-structure transitions in Ca-like Fe vii are calculated using an R-matrix method, which included the 80 terms arising from the 3d², 3d4s, 3d4p, 3d4d, 3d4f and 3p⁵3d³ configurations. Extensive autoionizing resonance structures together with channel coupling is therefore explicitly included; relativistic effects are accounted for by a term-coupling transformation. A thermal average is taken to obtain the effective fine-structure collision strength as a function of electron temperature T, for log T(K) = 4.3-6. Open 3p-shell resonances are seen to considerably enhance the background collision strength, by several factors for some of the 3d transitions.