Recombination lines (76 α) of hydrogen, helium, carbon and one other element from high-emission-measure H II regions

Twenty-five H II regions of relatively high emission measure have been observed with a telescope beam of half-power width 2.3 arcmin near 14.7 GHz (76α) for their radio recombination lines of hydrogen, helium, carbon and other elements. Spectra are presented together with observational and derived parameters. Electron temperatures and the helium abundance ratios $[N(\text{He}^+)/N(\text H^+)]$ and their distribution with galactic radius are discussed. No correlation was found between the He+ abundance and galactic radius. Carbon recombination lines were detected in 20 sources; their radial velocities and those of the hydrogen lines are compared with the velocities of several molecular species observed in the directions of the same sources. Lines of another element, assumed to be sulphur, were detected in four sources.