Collision Strengths for Electron Collision Excitation of Fine‐Structure Levels in Siii

Abstract

Electron collisional excitation strengths for transitions between the 3s23p2 3P0,1,2, 1D2, and 1S0 levels and from these levels to the fine-structure levels of the excited 3s3p3, 3s23p3d, 3s23p4s, 3s23p4p, and 3s23p4d configurations of S III are calculated in R-matrix approach. We considered 49 fine-structure levels arising from the 27 LS 3s23p2 3P, 1D, 1S, 3s3p3 5, 3So, 1, 3Do, 1, 3Po, 3s23p3d 1, 3Po, 1,3Do, 1, 3Fo, 3s23p4s 1,3Po, 3s23p4p 1,3S, 1,3P, 1,3D, 3s23p4d 1,3Po, and 1,3Do states. These target levels are represented by fairly extensive configuration-interaction wave functions. The collision strengths for transitions between fine-structure levels are calculated by transforming the LS-coupled K-matrices to K-matrices in an intermediate coupling scheme. Complicated resonance structures converging to excited state thresholds are explicitly included in collision strengths. The effective collision strengths are obtained from the total collision strengths by integrating over a Maxwellian velocity distribution. These are tabulated over a wide electron temperature range (0.5-10) × 104 K.