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Helium-like ions provide the most important X-ray spectral diagnostics inhigh temperature fusion and astrophysical plasmas. We previously presentedcomputed collision strengths for O~VII including relativistic fine structure,levels up to the $n=4$ complex and radiation damping of autoionizingresonances. We have extended this work to other He-like ions (N, Ne, Mg, Al,Si, S, Ca). The calculations are carried out using the Breit-Pauli R-matrix(BPRM) method with a 31-level eigenfunction expansion. Collision strengths forthe principal lines important in X-ray plasma diagnostics, w, x, y and z,corresponding to the 4 transitions to the ground level 1s^2(^1S_0) <-1s2p(^1P^o_1), 1s2p(^3P^o_2), 1s2p(^3P^o_1), 1s2s(^3S_1), are explicitly shown.We find the effect of radiation damping to be significant for the forbiddentransitions in heavier He-like ions, which should affect the diagnostic lineratios. We extrapolated the collision strengths to their values at infiniteenergy using the Burgess-Tully extrapolation technique. This is required tocalculate the Maxwellian average collision strengths at high temperature. Weshow that the coupling between dipole allowed and inter-combination transitionsaffects increasingly the effective collision strengths for the n ^1S_0 - n'^3P_1 transition as the charge of the ion increases. This clearly affects thetreatment of the extrapolation toward the infinite energy point of thecollision strength. This work is carried out as part of the Iron Project-RmaXNetwork.Comment: 13 pages, 6 figures, submitted to J.Phys.

Electron impact excitation of helium-like ions up ton= 4 levels including radiation damping