THz SPECTROSCOPY OF H$_2$D$^+$
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Date
2009
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Ohio State University
Abstract
The pure rotational transition frequencies of H$_2$D$^+$, $2_{12}\leftarrow 1_{11}, 2_{02}\leftarrow 1_{01}, 2_{11}\leftarrow 1_{10}$, and $3_{13}\leftarrow 2_{12}$, have been measured in the laboratory precisely by using a tunable far-infrared spectrometer. Among them, the $2_{12}\leftarrow 1_{11}$ line was recently detected in space toward Sgr B2 by Cernicharo {\it et al.}$^a$. Their identification was made based on a calculated line frequency estimated from the spectroscopic data of Amano and Hirao$^b$. It has been found that our measured frequency of this line, 2363242.82(69) MHz, is lower by about 20 MHz than the estimated value. All the available THz lines and known millimeter- and submillimeter-wave lines together with the combination differences derived from the infrared transitions are fitted to the Watson effective Hamiltonian. A set of improved molecular constants are obtained. \\ ----------------------------------------\\ $^a$J.Cernicharo, E. Polehampton, and J.R. Goicoechea. {\it Astrophys. J.}, {\bf 657}, L21-L24 (2007).\\ $^b$T. Amano and T. Hirao, {\it J. Mol. Spectrosc.}, {\bf 233}, 7-14 (2005).\\
Description
Author Institution: Department of Physics, University of Toyama, Gofuku, Toyama 930-8555, Japan; Department of Chemistry, University of Waterloo, Waterloo, Canada N2L 3G1