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W.M. Irvine, A.J. Lovell, M. Senay (Astronomy, UMass), H.E. Matthews (NRC Canada \& JAC), R.B. Metz (Chemistry, UMass), R. Meier (IfA, UHawaii), D. McGonagle (Pope John XXIII Natl. Seminary)
The chemistry of both nitrogen and sulfur present interesting problems in comets. We report here the first detection of a coma molecule which contains both these elements, the nitrogen sulfide (NS) radical. Using the JCMT, both lambda-doublet components of the J = 15/2 - 13/2 transition of NS at 346 GHz were observed in comet Hale-Bopp, leaving no doubt about the identification. A column density in the 14 arcsec beam is calculated to be about N = 7 x 1012 cm-2 on March 22, 1997, when the comet was at a heliocentric distance of 0.932 AU and a geocentric distance of 1.315 AU. Determination of a production rate requires knowledge of the unknown distribution of NS in the coma. Haser model calculations for a wide range of NS and possible parent lifetimes lead to a lower limit on the production rate, relative to water, of a couple of hundredths of a percent. A possible parent for NS is thionitrosyl hydride (HNS), which is expected to be stable at the low temperatures of cometary nuclei, but which has not had its structure or spectrum studied in the laboratory. An alternative may be thionylimide (HNSO), which is reasonably stable at laboratory temperatures. This research was supported in part by NASA grants NAG5-3653 and NAG5-6612.