The Si II intercombination multiplet in late-type stars

Abstract

New atomic data are used to calculate the relative intensities of transitions within the Si II|$3{s}^{2}3{p}^{2}P-3s3{p}^{2}\,^{4}{P}$| intercombination multiplet for plasma parameters appropriate to late-type stellar atmospheres. These ratios are found to be significantly different from those of Dufton & Kingston, principally due to changes in the radiative rates. A comparison with line ratios for the Sun (from Skylab S082B spectra) and late-type stars (from IUE data) indicates that although the new theoretical line ratios are in better agreement with observation, significant discrepancies still exist. Possible explanations for these discrepancies are briefly discussed.