Hydrogen Chloride Detection in Orion A and Monoceros R2 and Derivation of the H 35Cl/H 37Cl Isotopic Ratio

Abstract

view Abstract Citations (22) References (55) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Hydrogen Chloride Detection in Orion A and Monoceros R2 and Derivation of the H35Cl/H37Cl Isotopic Ratio Salez, M. ; Frerking, M. A. ; Langer, W. D. Abstract We have detected the J = 1-0 transition of H35Cl in the Orion A and Monoceros R2 giant molecular clouds, using the Caltech Submillimeter Observatory and a new heterodyne receiver built at the Jet Propulsion Laboratory. We find a llCl fractional abundance of a few times 10-10 and a depletion of gas- phase chlorine by a factor of 550-640 for Orion and 65-125 for Mon R2. For both sources, we derived the line optical depth and excitation temperature using the relative intensities of the hyperfine components and determined the abundance and excitation conditions with a large velocity gradient (LVG) model. The LVG model indicates that radiative pumping of the molecules by moderately warm dust is required to explain the observed line intensities and optical depths. In addition, we report the first detection of the isotope H37Cl from its J = 1-0 emission in Orion. Because the chemical reactions involving hydrogen chloride in molecular clouds are relatively simple, [H35Cl]/[H37Cl] is believed to provide a good estimate of [35Cl]/[37Cl]. We find an isotopic ratio about 1.3-2 times that of the solar neighborhood, suggesting that this ratio is not constant throughout the galactic interstellar medium. Publication: The Astrophysical Journal Pub Date: August 1996 DOI: 10.1086/177646 Bibcode: 1996ApJ...467..708S Keywords: ISM: MOLECULES; ISM: ABUNDANCES; ISM: INDIVIDUAL NAME: ORION; ISM: INDIVIDUAL NAME: MONOCEROS R2; RADIO LINES: ISM full text sources ADS | data products SIMBAD (17)