Knowledge Bank

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 $\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}C18O,O2(1\Delta g),HN2+$ and their isotopes are used for assessing the sensitivity of the system. The sensitivity of our system is found to be about $2\times 10-7$ with 1 sec time constant and with 1.5 m path length. It corresponds to minimum detectable absorption coefficient of $1.3\times 10-9cm-1$.