view Abstract Citations (28) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Isotopic fractionation and mass motion in giant molecular clouds. Penzias, A. A. Abstract Millimeter-wave rotation spectra of the 12C16O, 13C16O, and 12C18O isotopes of carbon monoxide were mapped in two giant molecular clouds in the Galaxy, NGC 2264 and W3(OH). The data were used to derive 13C16O/12C18O abundance ratios as a function of velocity, as well as position, in these sources. These observations show that carbon-13 isotopic abundance determinations are more subject to chemical enhancement effects than had been previously realized. There is a suggestive association between velocity wings and cloud edges, which fits predictions of cloud evolution models involving large-scale radial motion. Measurements of the rare 13C18O species were also made in these two clouds and a new interstellar 12C/13C abundance (100±14) was derived. Publication: The Astrophysical Journal Pub Date: October 1983 DOI: 10.1086/161358 Bibcode: 1983ApJ...273..195P Keywords: Abundance; Astronomical Spectroscopy; Carbon Isotopes; Interstellar Chemistry; Molecular Clouds; Carbon Monoxide; Chemical Fractionation; Milky Way Galaxy; Molecular Rotation; Rotational Spectra; Astrophysics full text sources ADS | data products SIMBAD (2)