DETECTION OF $D_{2}H^{+}$ IN THE DENSE INTERSTELLAR MEDIUM

Author Institution: Downs Laboratory of Physics, California Insitiutre of Technology; Caltech Submillimeter Observatory, California Insitiutre of TechnologyThe 692 GHz para ground-state line of $D_{2}H^{+}$ has been detected at the Caltech Submillimeter Observatory towards the pre-stellar core 16293E. The derived $D_{2}H^{+}$ abundance is comparable to that of $H_{2}D^{+}$, as determined by observations of the 372 GHz line of ortho$-H_{2}D^{+}$. 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 $H_{3}^{+}$ were missing factors of earlier models. The inclusion of $D_{2}H^{+}$ and $D_{3}^{+}$ in the models leads to predictions of higher values of the D/H ratio in the gas phase