Electron Impact Excitation Rates for Transitions from the Ground State to then= 2 and 3 levels in Helium-Like Ions

Electron excitation rates for the ground state to n = 2 and 3 S and P levels in He-like ions between F VIII and Mn XXIV have been determined by interpolating recent R-matrix and distorted wave calculations for O VII, Mg XI, Ca XIX and Fe XXV. Results are presented in the form of polynomial fits in log T e to the effective collision strengths (γ) for each transition. The fits may be used to estimate values of γ accurate to between 10 and 20% over a temperature range approximately equal to log T max ± 0.8 dex, where T max is the temperature of maximum fractional abundance in ionisation equilibrium of the relevant species.