Electron Impact Excitation Rates for Beryllium-Like Ions

Electron excitation rates for all transitions amongst the 2s^{2 1}S^e; 2s2p ³P⁰, ¹P, 2p^{2 3}P^e, ¹D^e and ¹S^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.