Frost, R. L.; Beckman, J. E.; Watt, G. D.; White, G. J. and Phillips, J. P.
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The abundance ratio of D:H in the interstellar medium can be derived either more directly from the UV absorption measurements of HD and H2 in the spectra of early-type stars, or less directly from millimeter-wave emission in the rotational lines of a variety of molecules. The latter method is applicable over a much larger portion of the galaxy, but is subject to the uncertainty inherent in chemical fractionation. It is shown here how the basic assumptions of temperature distribution and geometry within a single source can cause the derived ratio HDO:H2O to vary between 0.05 and 0.0025, a comparable range to that found with three different molecules DCN:HCN, DNC:HNC, and DCO+:HCO+ in the same source. This result should lead to caution in the interpretation of such abundance ratios and of their gradients within the galaxy.
|Item Type:||Book Chapter|
|Copyright Holders:||1982 Not known|
|Keywords:||abundance; astronomical spectroscopy; cosmochemistry; deuterium; interstellar matter; milky way galaxy; molecular spectroscopy; temperature distribution|
|Academic Unit/Department:||Science > Physical Sciences|
|Interdisciplinary Research Centre:||Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)|
|Depositing User:||Glenn White|
|Date Deposited:||06 Jun 2012 13:37|
|Last Modified:||06 Jun 2012 13:37|
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