Atomic data from the IRON Project - XXXVI. Electron excitation of Be-like Fe XXIII between 1s(2)2l(1)2l(2) SLJ and 1s(2)2l(3)2l(4) S ' L ' J '

Partial collision strengths for electron induced transitions in the berylli um-like ion Fe XXIII are calculated using the Belfast R-matrix programs (Be rrington et al. 1995). Our target has 98 fine structure states 1s(2)nln'l' SLJ corresponding to n = 2 and n' = 2,3,4. The present calculation is carri ed out for electron impact energies in the range 3.15 to 350 Ry. Below 115. 185 Ry, corresponding to the highest excited state of our model ion, we use the Breit-Pauli version of the R-matrix code. For energies between 116 and 350 Ry we use the nonrelativistic LS-coupling version of the R-matrix code together with JAJOM (Saraph 1978). When T exceeds about ten million degree s one needs to take account of contributions to the thermally averaged coll ision strength Y coming from electrons with energies in excess of 350 Ry. W e discuss a way of estimating these contributions. Values of Y are computed and tabulated as functions of log T for transitions between the 2s(2) S-1( 0), 2s2p P-3(0,1,2)o, 2s2p P-1(1)o, 2p(2) P-3(0,1,2) 2p(2) D-1(2) and 2p(2) S-1(0) states. The temperature range 6.3 less than or equal to log T less than or equal to 8.1 is centred on log T = 7.1 which, according to Arnaud & Rothenflug (1985), is where Fe XXIII has maximum coronal abundance.