2004ApJ...606L.127V

The 692 GHz para ground-state line of D₂H⁺ has been detected at the Caltech Submillimeter Observatory toward the prestellar core 16293E. The derived D₂H⁺ abundance is comparable to that of H₂D⁺, as determined by observations of the 372 GHz line of ortho-H₂D⁺. This is an observational verification of recent theoretical predictions, developed to explain the large deuteration ratios observed in cold, high-density regions of the interstellar medium associated with low-mass prestellar cores and protostars. This detection confirms expectations that the multiply deuterated forms of H⁺₃were missing factors of earlier models. The inclusion of D₂H⁺ and D⁺₃ in the models leads to predictions of higher values of the D/H ratio in the gas phase.