Collision strengths for electron impact excitation with Ca XV: a relativistic approach

Collision strengths for electron impact excitation between the lowest 20 levels among the 1s 2 2s 2 2p 2 , 2s2p 3 and 2p 4 configurations of Ca XV have been computed for collision energies of 15, 30, 45 and 60 Ryd in a Dirac-Fock approximation. Comparisons have been made with the R-matrix and distorted-wave collision strengths. Differences are discussed and the accuracy is assessed.