A&A Supplement series, Vol. 129, April I 1998, 161-172
Received July 17; accepted September 12, 1997
K.A. Berrington, H.E. Saraph, and J.A. Tully
The collision strength for the fine structure transition within the ground term of 17 fluorine-like ions from Mg IV to Ni XX is calculated using the R-matrix method. We include target terms with n = 3 in order to take account of the resonance structure in at energies above . These resonances are delineated using a fine mesh of several thousand energy points to scan the region between the first and 27th excited terms. Results from an earlier calculation (IRON Project Paper IV) are used to cover the region below . We make use of the fact that tends to the Born limit as the collision energy . The effective collision strength is tabulated as a function of log, where is a Z-scaled temperature. We compare results for Si+5, Fe+17 and Ni+19 with those obtained by Mohan and co-workers. An explanation is given for the large discrepancy in the case of .
keywords: atomic data -- atomic processes