title: Observations of H2S toward OMC-1.
abstract: Interstellar hydrogen sulfide (H2S) and its isotopic variant (H2(34)S) have been observed toward several positions in OMC-1 via their 1(10)-1(01) transitions near 168 GHz using the FCRAO 14 m telescope.  We derive total column densities toward Orion(KL) for the extended ridge, for the plateau, and for the hot core, in addition to values for other positions in OMC-1.  The fractional abundance of H2S (approximately 10(-9)) in the quiescent regions of OMC-1 seems to be difficult to explain by currently known ion-molecule reactions.  The fractional abundance of H2S relative to H2 is enhanced by a factor of 1000 in the hot core and the plateau relative to the quiescent clouds.  This enhancement may be a result of grain surface chemistry and/or of high-temperature gas-phase chemistry.  From the nondetection of HDS in its 2(11)-2(12) transition, we estimate the abundance ratio [HDS]/H2S] < or = 0.02 in the hot core.
authors.affiliation: Department of Physics and Astronomy, University of Massachusetts at Amherst, USA.
authors.forename: Y C
authors.initials: YC
authors.lastname: Minh
authors.forename: L M
authors.initials: LM
authors.lastname: Ziurys
authors.forename: W M
authors.initials: WM
authors.lastname: Irvine
authors.forename: D
authors.initials: D
authors.lastname: McGonagle
mesh_terms: D055580:Astronomical Phenomena; D001256:Astronomy; D055598:Chemical Phenomena; D002621:Chemistry; D005118:Extraterrestrial Environment; D006859:Hydrogen / Q000032:analysis; D006862:Hydrogen Sulfide / Q000032:analysis*; D013057:Spectrum Analysis; D013460:Sulfur Isotopes; D013696:Temperature
chemical_list: D013460:Sulfur Isotopes; D006859:Hydrogen; D006862:Hydrogen Sulfide