15min:

F. MATSUSHIMA, T. YONEZU, Y. MORIWAKI AND K. TAKAGI, Department of Physics, University of Toyama, Gofuku, Toyama 930-8555, Japan; T. AMANO, Department of Chemistry, University of Waterloo, Waterloo, Canada N2L 3G1.

The pure rotational transition frequencies of H₂D⁺, 2₁₂ 1₁₁, 2₀₂ 1₀₁, 2₁₁ 1₁₀, and 3₁₃ 2₁₂, have been measured in the laboratory precisely by using a tunable far-infrared spectrometer. Among them, the 2₁₂ 1₁₁ line was recently detected in space toward Sgr B2 by Cernicharo 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.
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^aJ.Cernicharo, E. Polehampton, and J.R. Goicoechea. Astrophys. J. , 657, L21-L24 (2007).
^bT. Amano and T. Hirao, J. Mol. Spectrosc. , 233, 7-14 (2005).