Electron Collisional Excitation of S XII

Abstract

Atomic data have been obtained for the coronal ion S XII using the UCL program codes. Energy levels and radiative transition probabilities have been computed with different target descriptions allowing for configuration interaction and relativistic effects. Multi-configuration Hartree-Fock method is used to calculate the target wave functions. Collisional excitation cross sections between the 2 s2 2 p 2P0, 2s2p2 4P, 2D, 2S, 2P and the 2p3 4S0, 2D0, 2P0 eigenstates of S XII have been calculated using eight-state close coupling and distorted wave approximations with a target description employing a 3̄̄̄d̅ pseudo orbital. Collision strengths between the lowest five eigenstates of S XII have also been computed in five-state close coupling and distorted wave approximations for comparison. The results are compared with available theoretical work. It is found that the use of elaborate target wave functions and the choice of a more accurate scattering approximation may change the cross sections by more than 25% in some of the transitions