# HIGH-SENSITIVE SUB-MILLIMETER WAVE SPECTROSCOPY OF IONS AND FREE RADICALS

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 Title: HIGH-SENSITIVE SUB-MILLIMETER WAVE SPECTROSCOPY OF IONS AND FREE RADICALS Creators: Akao, K.; Oka, T.; Amano, T. Issue Date: 1997 Publisher: Ohio State University Abstract: Sub-millimeter wave spectroscopy in the frequency range of over 500 GHz has not been a territory of easy access. A number of space sub-millimeter wave telescopes are launched or planned, and in view of imminent collaboration between astronomy and laboratory spectroscopy, a sub-millimeter wave spectrometer system has been constructed with Russian made BWOs as radiation sources. Frequency ranges of 570-700 GHz and 770-840 are covered with two BWOs. The sub-millimeter wave frequency is phase-locked to harmonics of a millimeter wave radiation generated by a Gunn oscillator. The sub-millimeter wave harmonic mixer was fabricated in K\""{o}ln, a similar one used in G. Winnewisser’s $group.^{m}$ Unstable molecular species are generated either in an extended negative glow discharge cell or a hollow cathode discharge cell which can be cooled down to $-80^{\circ}$C. Several stable and unstable molecules such as $^{12}C^{18}O, O_{2}(^{1}\Delta_{g}), HN^{+}_{2}$ and their isotopes are used for assessing the sensitivity of the system. The sensitivity of our system is found to be about $2\times10^{-7}$ with 1 sec time constant and with 1.5 m path length. It corresponds to minimum detectable absorption coefficient of $1.3\times10^{-9} cm^{-1}$. Description: $^{m}$See, for example, S. P. Below, F. Lewen, Th. Klaus, and G. Winnewisser, J. Mol. Spectrosc. 174, 606 (1995). Author Institution: Institute for Astrophysics and Planetary Sciences, Ibaraki University URI: http://hdl.handle.net/1811/13986 Other Identifiers: 1997-RH-06