DETERMINATION OF THE HE+/H+ RATIO FROM ALPHA-RADIO, BETA-RADIO, AND GAMMA-RADIO RECOMBINATION LINES

We report high signal-to-noise ratio observations of the 91-alpha, 114-beta, and 130-gamma-hydrogen and helium radio recombination lines toward several Galactic H II regions. These observations were used to determine the ionized helium-to-ionized hydrogen abundance ratio by number, y+. Since the observations were made with the same radio telescope at approximately the same frequency, we consider them to be practically free of beamwidth and frequency effects. For a given source, we find y+ values consistent within error for the different n values measured.