Deuterated chemistry of the early universe

Fractional abundances for each are calculated as a function of redshift z in the recombination era. The abundances of the isotopologues are found to display similar behavior.

Fractionation enhances the abundances of most of the more highly deuterated species as the redshift decreases due to the closing of some reaction channels as the gas temperature cools. Rate coefficients for the majority of the reactions involving the deuterated species are uncertain resulting in a corresponding uncertainty in their predicted abundances.