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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.

Nitric oxide has been newly detected towards several star-forming clouds, including Orion-KL, Sgr B2(N), W33A, W51M, and DR21(OH) via its J = 3/2 --> 1/2 transitions near 150 GHz, using the FCRAO 14 m telescope. Both lambda-doubling components of NO were observed towards all sources. Column densities derived for nitric oxide in these clouds are N approximately 10(15)-10(16) cm-2, corresponding to fractional abundances of f approximately 0.5-1.0 x 10(-8), relative to H2. Towards Orion-KL, the NO line profile suggests that the species arises primarily from hot, dense gas. Nitric oxide may arise from warm material toward the other clouds as well. Nitric oxide in star-forming regions could be synthesized by high-temperature reactions, although the observed abundances do not disagree with values predicted from low-temperature, ion-molecule chemistry by more than one order of magnitude. The abundance of NO, unlike other simple interstellar nitrogen compounds, does appear to be reproduced by chemical models, at least to a good approximation. Regardless of the nature of formation of NO, it appears to be a common constituent of warm, dense molecular clouds. N-O bonds may therefore be more prevalent than previously thought.

We present the aperture synthesis imaging of and HCO`1È0 lines and of continuum C 3 H 2 2 12 È1 01 emission at j \ 3.4 mm toward the class 0 young stellar object IRAS 18148[0440 in the L483 molecular cloud. The continuum emission is detected at the IRAS position at a level of 16 mJy, indicating a compact source with a mass of D0.13The delineates an envelope near the IRAS position, M _ . C 3 H 2 with a size of D 3000 AU ] 2000 AU in R.A. and decl. directions, respectively. A velocity gradient detected only along the axis of outÑow can be explained in terms of free-fall motion of the envelope. The HCO`line wing extends up to the velocity of^6 km s~1 relative to the systemic one, and the highvelocity material shows a symmetric bipolarity and extends over 2@ or 0.1 pc along the east-west direction. It is found that the outÑow material is clumpy and the opening angle is widest for the slowest moving component. The core component of the HCO`1È0 line exhibits an anti-infall asymmetry not only in interferometric but also in single dish observations. It is attributable to the slow isotropic outward motion of gas between the Ñattened envelope and the collimated outÑow.