Physics
Scientific paper
Oct 1986
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1986inpr.conf..153z&link_type=abstract
In NASA. Ames Research Center Summer School on Interstellar Processes: Abstracts of Contributed Papers p 153-154 (SEE N87-15043
Physics
Infrared Absorption, Interstellar Gas, Molecular Clouds, Molecular Excitation, Vibrational Spectra, Acetonitrile, Activation Energy, Chemical Reactions, Cyanoacetylene, Hydrocyanic Acid, Interstellar Chemistry, Stellar Evolution
Scientific paper
Several molecules thus far have been detected in the ISM in vibrationally-excited states, including H2, SiO, HC3N, and CH3CN. In order for vibrational-excitation to occur, these species must be present in unusually hot and dense gas and/or where strong infrared radiation is present. In order to do a more thorough investigation of vibrational excitation in the interstellar medium (ISM), studies were done of several mm-wave transitions originating in excited vibrational modes of HCN, an abundant interstellar molecule. Vibrationally-excited HCN was recently detected toward Orion-KL and IRC+10216, using a 12 meter antenna. The J=3-2 rotational transitions were detected in the molecule's lowest vibrational state, the bending mode, which is split into two separate levels, due to l-type doubling. This bending mode lies 1025K above ground state, with an Einstein A coefficient of 3.6/s. The J=3-2 line mode of HCN, which lies 2050K above ground state, was also observed toward IRC+10216, and subsequently in Orion-KL. Further measurements of vibrationally-excited HCN were done using a 14 meter telescope, which include the observations of the (0,1,0) and (0,2,0) modes towards Orion-KL, via their J=3-2 transitions at 265-267 GHz. The spectrum of the J=3-2 line in Orion taken with the 14 meter telescope, is shown, along with a map, which indicates that emission from vibrationally-excited HCN arises from a region probably smaller than the 14 meter telescope's 20 arcsec beam.
Erickson Neal R.
Snell Ronald L.
Ziurys Lucy M.
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