15min:

R. FUJIMORI, K. KAWAGUCHI, Department of Chemistry, Faculty of Science, Okayama University, 3-1-1, Tsushima-Naka, Okayama 700-8530, Japan; T. AMANO, Department of Chemistry and Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada.

Five pure rotational transitions of H₂F⁺ were observed in the 473-774 GHz range with a backward-wave oscillator based submillimeter-wave spectrometer. The H₂F⁺ ion was generated in an extended negative glow discharge in a gas mixture of hydrogen fluoride generated by heating potassium hydrogen fluoride (HF₂K) granular powder at 150^oC-160^oC and hydrogen in an argon buffer. A simultaneous analysis of the rotational lines with 120 combination differences for the ground state derived from the infrared spectra obtained by Schäfer and Saykally\footnoteE.~Schäfer and R.~J.~Saykally, J.~Chem.~Phys. , 81,~4189~(1984) and Fujimori et al.\footnoteR. Fujimori, Y. Hirata, K. Kawaguchi, and I. Morino, RE02, The 65^th OSU International Symposium on Molecular Spectroscopy~(2010)(Columbus, OH) was carried out to determine the precise molecular constants for the ground state. The rotational transition frequencies that lie below 2 THz were calculated, together with their estimated uncertainties, to facilitate future astronomical identifications. Recently H₂Cl⁺ was detected in NGC 6334I and Sgr B2 with the Heterodyne Instrument for Far-Infrared (HIFI) on board the Herschel Space Observatory\footnoteD.~C. Lis et~al ., Astron. Astrophys. , 521,~L9~(2010), and HF was also detected in a wide variety of interstellar clouds with the same facility\footnoteD. A. Neufeld et al. , Astron. Astrophys. , 518, L108 (2010); T. G. Phillips et al. , Astron. Astrophys. , 518, L109 (2010); P. Sonnentrucker et al. , Astronon. Astrophys. , 521, L12 (2010). The proton affinity of HF is smaller than those of N₂ and CO, so the abundance of H₂F⁺ is likely to be low in dense molecular clouds. We will discuss abundances of H₂F⁺ in diffuse molecular clouds, considering various chemical reaction rates.