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First Detection of OD outside the Solar System

First Detection of OD outside the Solar System. Parise et al. 2012, A&A. In cold and dense clouds, chemical reactions forming molecules with Hydrogen prefer the isotope Deuterium. This process, called fractionation, leads to relatively high abundances of deuterated molecules.

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First Detection of OD outside the Solar System

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  1. First Detection of OD outside the Solar System Parise et al. 2012, A&A • In cold and dense clouds, chemical reactions forming molecules with Hydrogen prefer the isotope Deuterium. This process, called fractionation, leads to relatively high abundances of deuterated molecules. • Fractionation is driven by the fact that the heavier molecule (OD) has a lower energy ground state than the lighter one (OH) • SOFIA/GREAT observations detected OD, the deuterated form of the hydroxyl radical, OH, which is important in the chemical pathway for forming water, in the protostar IRAS 16293-2422. Ground state transition: Sensitive to cold gas OD J=5/2->3/1 transition observed toward protostar IRAS16293, smoothed to 0.79 km/s

  2. First Detection of OD outside the Solar System • SOFIA observations were made with the German Receiver at Terahertz frequencies (GREAT) • Herschel recently detected ND, the deuterated form of NH, and found a very high fractionation (Bacmann et al. 2010), but • Herschel could not observe OD because it was outside the frequency range of its HIFI spectrometer. • The SOFIA spectrum of OD shows a similar velocity profile to the Herschel spectrum of deuterated water, HDO, after taking into account the hyperfine structure of OD (red bars). • The inferred abundance of OD is 17-90 times more than HDO, higher than predicted by chemistry models • Interpretation would benefit from improved measurement of OD collision rates

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