Atomic data from the IRON Project

Collision strengths for electron induced transitions in the beryllium-like ion Fe+22 are calculated using the intermediate coupling frame transformation (ICFT) version of the R-matrix programs. Our target has 98 fine structure states corresponding to and . The present calculation is for electron impact energies in the range 3.15 to 380 Ry. When T exceeds about ten million degrees one needs to take account of contributions to the thermally averaged collision strength coming from electrons with energies in excess of 380 Ry. We discuss a way of allowing for these contributions. Values of for all the transitions between the ground state and the excited states , with are tabulated as a function of . The temperature range is centred on which is approximately where Fe+22 has maximum abundance in ionization equilibrium. To the best of our knowledge these are the first R-matrix calculations for Fe+22 for excitations to the levels. Good agreement with previous distored-wave calculations is found. However, the resonance contributions have an important effect on the effective collision strengths and in turn on the level populations.