Atomic data from the IRON Project

Abstract

The collision strength ( 2 P o=2 ; 2 P o=2 )f or the ne 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 withn =3 in order to take account of the resonance structure in at energies above 2s2p 62 S. These resonances are delineated using a ne mesh of several thousand energy points to scan the region between the rst and 27th excited terms. Results from an earlier calculation (IRON Project Paper IV) are used to cover the region below 2s2p 62 S. We make use of the fact that tends to the Born limit as the colli- sion energy E!1. The eective collision strength is tabulated as a function of logTs ,w here T s =T= (Z 8) 2 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 (Si +5 ).