DETECTION OF INTERSTELLAR N2O - A NEW MOLECULE CONTAINING AN N-O BOND

A new interstellar molecule, N2O, known as nitrous oxide or ''laughing gas,'' has been detected using the NRAO 12 m telescope. The J = 3 --> 2, 4 --> 3, 5 -->, 4, and 6 --> 5 rotational transitions of this spec ies at 75, 100, 125, and 150 GHz, respectively, were observed toward S gr B2(M). The column density derived for N,O in this source is N-lot s imilar to 10(15) cm(-2), which corresponds to a fractional abundance o f similar to 10(-9), relative to H-2. This value implies abundance rat ios of N2O/NO similar to 0.1 and N2O/HNO similar to 3 in the Galactic center. Such ratios are in excellent agreement with predictions of ion -molecule models of interstellar chemistry using early-time calculatio ns and primarily neutral-neutral reactions. N,O is the third interstel lar molecule detected thus far containing an N-O bond. Such bonds cann ot be so rare as previously thought.