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Title:The interstellar detection of CH3NCO in Sgr B2(N)
Author(s):Halfen, DeWayne T.
Contributor(s):Ziurys, Lucy M.; Ilyushin, V.
Abstract:A new interstellar molecule, CH$_3$NCO (methyl isocyanate), has been detected for the first time using the 12 m telescope of the Arizona Radio Observatory (ARO). CH$_3$NCO was identified in spectra covering 68 - 116 GHz in the 3 mm segment of a broadband survey of Sgr B2(N). This study was based on previous laboratory work by Koput (1986) and new Fourier transform millimeter-wave (FTmmW) measurements performed at Arizona in the 60 - 88 GHz range. Spectroscopic constants were determined for CH$_3$NCO in a combined fit, and were used to predict other transitions at 3 mm. Thirty very favorable rotational lines (K$_a$ = 0 and K$_a$ = 1 only
E$_u$ $<$ 60 K) originating in five consecutive transitions of CH$_3$NCO in both the A and E internal rotation states were found to be present in the Sgr B2(N) survey from 68 - 105 GHz. Emission was observed at all of the predicted frequencies, with 17 lines appearing as distinct, uncontaminated spectral features, clearly showing the classic a-type, asymmetric top pattern. The CH$_3$NCO spectra also appear to exhibit two velocity components near V$_{LSR}$ $\approx$ 62 and 73 km s$^{-1}$, both with $\Delta$V$_{1/2}$ $\approx$ 10 km s$^{-1}$, typical of most molecules in Sgr B2(N). The fractional abundances were determined to be $f$ = 7.6 x 10$^{-12}$ and 5.0 x 10$^{-12}$ for the 62 and 73 km s$^{-1}$ components, relative to H$_2$, respectively. CH$_3$NCO was recently detected in volatized material from comet 67P/Churyumov-Gerasimenko by Rosetta's Philae lander.
Issue Date:2016-06-22
Publisher:International Symposium on Molecular Spectroscopy
Genre:Conference Paper/Presentation
Rights Information:Copyright 2016 by the authors
Date Available in IDEALS:2017-01-26

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