title: Interstellar sulfur hydride: a search for the 111-megahertz lines.
abstract: Similarities in the energy-level structure of the sulfur hydride radical and the hydroxyl radical suggest that sulfur hydride in the interstellar medium might be detectable because of a population inversion or anti-inversion similar to that of the hydroxyl radical. We have searched for the 111.54-megahertz transition [F (total angular momentum quantum number) = 2 --> 2] and for the 111.22-megahertz transition (F = 1 --> 1) in the galactic radio source W49, one of the brightest hydroxyl emission sources. No sulfur hydride emission lines with half-power widths of 130 hertz or greater were detected with the 1000-foot Arecibo antenna. The upper limits established with 100-hertz filters were 50 and 60 flux units (1 flux unit= 10(26) watt meter(-2) hertz(-1)), respectively, for the two lines.
authors.forename: M L
authors.initials: ML
authors.lastname: Meeks
authors.forename: M A
authors.initials: MA
authors.lastname: Gordon
authors.forename: M M
authors.initials: MM
authors.lastname: Litvak