Theoretical He I line intensities in low-density plasmas

A capture-collision-cascade model has been developed for calculating recombination spectra of He I in nebular conditions. The method of solution closely follows the treatment of Brocklehurst (1972 Mon Not. R. Astr. Soc. 157, 211). The results of computations at temperatures from 312.5 to 20 000 K and electron densities Ne of 102, 104 and 106 cm-3 are presented. The singlets have been treated in both case A and B conditions, the triplets in case B only. The He I results use newer data than the calculations of Brocklehurst and highlight an error in his work. These calculations can be used to interpret the line emissions from He I in the optical and infrared bands. (author)