Oscillator strengths for transitions among the low-lying energy levels of S II

The authors report an accurate large-scale CI calculation of the oscillator strengths for transitions among the energy levels of the low-lying 3s23p3, 3s 23p2(3P)4p, 3s3p4, 3s23p2(3P)4s, and 3s23p2(3P)3d configurations of S II in the LS coupling approximation. Oscillator strengths for the astrophysically important transitions 3s23p3 4S degrees 3/2 to 3s3p4 4Pe 1/2,3/2,5/2 are calculated in intermediate coupling. These are small because of cancellation of relatively large contributions to the transition matrix elements from the 3s3p4 and 3s23p23d configurations in the final state. Nevertheless, the results have converged and lie within 5% of the oscillator strengths derived from a measurement of the lifetimes of the upper levels.