Knowledge Bank

The 692 GHz para ground-state line of $D2H+$ has been detected at the Caltech Submillimeter Observatory towards the pre-stellar 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 (Roberts, Herbst & Millar 2003), developed to explain the large deuteration ratios observed in cold, dense regions of the interstellar medium associated with low mass pre-stellar cores and protostars. This detection confirms expectations that the multiply deuterated forms of $H3+$ were missing factors of earlier models. The inclusion of $D2H+$ and $D3+$ in the models leads to predictions of higher values of the D/H ratio in the gas phase.