Recombination line intensities for hydrogenic ions: The fine-structure components of HI and HeII

Abstract

Emissivities have been calculated for fine-structure components of selected UV and optical recombination lines of HI and HeII. Results are given for a range of electron temperatures and densities, and in Cases A and B of Baker & Menzel (1938). Relative intensities, wavelengths and velocity shifts of the fine-structure components are tabulated. Applications to the spectra of gaseous nebulae are discussed. Depending on the temperature, density and Case, the centres of unresolved lines can shift by up to 0.9 kms-1 for HI and 3.3 kms-1 for HeII. A new calibration of the Hα-[NII] method for determining electron temperatures is given.