SIMBAD references

In this Letter, we present the first results from updated models of interstellar deuterium chemistry that now include all possible deuterated isotopomers of H⁺₃. We find that in regions of high density and heavy depletion, such as prestellar cores, the inclusion of HD⁺₂and D⁺₃ enhances the fractionation of ionic and neutral species significantly. Our models are the first to predict the very high atomic D/H ratios (≥0.3) necessary for grain-surface chemistry models to reproduce the high formaldehyde and methanol fractionation seen in star-forming regions.