Electron impact excitation rates for transitions in beryllium-like P XII, S XIII, CI XIV, Ar XV and K XVI

Abstract

Electron excitation rates for the Be-like ions Ne VII, Si XI and Ca XVII calculated with the R-matrix code are used to interpolate data for all transitions amongst the 2s2 1S, 2s2p 3P, 1P, 2p2 3P, 1D and 1S levels in P XII, S XIII, Cl XIV, Ar XV and K XVI. Results are presented in the form of polynomial fits in log Te to the effective collision strengths (γ) for each transition. These fits should lead to results accurate to approximately ± 10%, and are applicable over a temperature range of log Tmax ± 0.8 dex, where Tmax is the temperature of maximum fractional abundance in ionisation equilibrium of the relevant species. The present data for Ar XV are significantly different from the earlier distorted wave calculations of Bhatia et al.