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		| Paper: | 
		Chemical Models for Molecular Absorption Features | 
	 
	
		| Volume: | 
		156, Highly Redshifted Radio Lines | 
	 
	
		| Page: | 
		196 | 
	 
	
		| Authors: | 
		Gerin, M.; Roueff, E. | 
	 
	
	
		| Abstract: | 
		We present dark cloud chemical models, including deuterium fractionation, for the molecular absorption features. We show that models for cold, low density gas (n = 10^4 cm^{-3}, T = 20K) predict molecular abundances similar to the observed values, even for low metallicity gas. The HIP solution gives a better agrement than the LIP solution since it predicts a low relative abundance of O_2 and a high abundance of CCH, as observed. The deuterium fractionation is proportional to the elemental deuterium abundance in the gas, and is lower in the HIP than in the LIP, by a factor ranging from 5 to 10. | 
	 
	
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