Electron Impact Excitation Rates for Beryllium-Like Ions

Electron excitation rates for all transitions amongst the 2 s 2 1 S e ; 2 s 2 p 3 P 0 , 1 P , 2 p 2 3 P e , 1 D e and 1 S e levels in Be-like N IV, F VI, Na VIII, Mg IX and Al X have been determined by interpolating similar data for C III, O V, Ne VII and Si XI that were calculated using the R-matrix method. Results are presented as polynomial fits in log T e to the effective collision strengths (γ) for each transition. These fits should lead to values of γ accurate to approximately ± 10% over a temperature range of ± 0.8 dex about log T max , where T max is the temperature of maximum fractional abundance in ionisation equilibrium of the species concerned.