C III observable with IUE.

Abstract

Theoretical emissivity ratios are presented for the C III UV multiplets at 977, 1176, 1247, 1908, and 2297 A. Proton-ion collision rates for the relevant transitions are calculated by using the semiclassical impact-parameter method as developed by Sahal-Brechot (1969). IUE observations of these multiplets in the planetary nebula NGC 7027, the slow nova RR Tel, and the quasar Q 1011 plus 25 are discussed, and electron densities are estimated.