10min:

ISAMU MORIN AND KOICHI M. T. YAMADA, National Institute for Advanced Interdisciplinary Research, Higashi 1-1-4, Tsukuba 305-8562, Japan.

\hspace*5mmA submillimeter-wave spectrometer using a BWO (Backward Wave Oscillator) has been constructed and applied to measurements for shrot-lived species. The BWO frequency was stabilized by a phase-lock loop, using a Schottky-type harmonic mixer which mixes the radiation from the BWO with that of a millimeter-wave synthesizer¹. A part of submillimeter power was reflected by a wire-grid beam-splitter and directed to the absorption cell. The transmitted power was detected by a magnetically-tuned, liquid-helium-cooled InSb bolometer. To test performances of the spectrometer, the rotational spectra of NH₂OH, NH₂, and CF have been measured in 400 -- 500 and 600 -- 800 GHz region.

\hspace*5mmThe NH₂ radical is known to be an important intermediate in astrochemistry and various chemical reaction process. The submillimeter-wave absorption spectrum was observed toward the dust continuum source Sagittarius B2². Recently, Tonooka et al. have measured the microwave spectrum and determined precise molecular constants³.

\hspace*5mmNH₂OH has been interested because of its large amplitude internal motions. The submillimter-wave rotational spectra in the ground and vibrationally excited OH-torsion state have been observed for the first time.

\hspace*5mmThe accuracy of submillimeter-wave line positions of the CF radical reported previously using a far-infrared laser sideband spectrometer is not enough to perform astronomical searches for this radical. In the present study the submillimeter-wave spectra of CF have been measured with same precision as microwave spectroscopy. \vspace*2mm

^aDomestic Research Fellow of Japan Science and Technology Corporation.

¹G. Winnewisser, Vib. Spectrosc. , 8, 241 (1995); I. Morino et al., J. Mol. Spectrosc. , 185, 142 (1997). ²E. F. van Dishoeck et al., Astrophys. J. , 416, L83 (1993). ³M. Tonooka et al. , J. Chem. Phys. , 106, 2563 (1997).