Emission line ratios for C III in the sun

Theoretical electron-density-sensitive C III emission line ratios are presented forR ₁ =I(2s2p ³ P – 2p ^{2 3} P)/I(2s2p ¹ P – 2p ^{2 1} S) =I(1176 Å)/I(1247 Å),R ₂ =I(2s2p ³ P – 2p ^{2 3} P)/I(2s ^{2 1} S – 2s2p ³ P ₁) =I(1176 Å)/I(1908 Å), andR ₃ =I(2s2p ¹ P – 2p ^{2 1} S)/I(2s ^{2 1} S – 2s2p ³ P ₁) =I(1247 Å)/I(1908 Å). These are significantly different from those deduced previously, principally due to the adoption of improved electron impact excitation rates in the present analysis. Electron densities deduced from the present theoretical line ratios, in conjunction with observed values ofR ₁,R ₂, andR ₃ measured from solar spectra obtained by the Naval Research Laboratory's S082B instrument on boardSkylab, are found to be generally compatible. In contrast, previous diagnostic calculations imply electron densities fromR ₁,R ₂, andR ₃ that differ by up to two orders of magnitude. These results provide observational support for the accuracy of the atomic physics adopted in the present calculations, and the methods employed in the derivation of the theoretical line ratios.