A COAXIALLY ORIENTED BEAM-RESONATOR ARRANGEMENT FOURIER TRANSFORM MICROWAVE (COBRA-FTMW) SPECTROMETER; GOING CRYOGENIC
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Date
1997
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Publisher
Ohio State University
Abstract
After the initial experiments of microwave spectroscopy in the time $domain^{g}$ it took more than two decades before the technique was re-born. First as a steady gas-$waveguide^{h}$, later as a molecular beam-$resonator^{i}$ application, the experiment became an established spectroscopic oriented beam-resonator arrangement (COBRA)$^{jk}$ has dramatically improved the resolution and the sensitivity of the Fourier transform microwave (FTMW) spectrometer. Our current efforts are aiming at an improvement of the COBRA-FTMW sensitivity by means of reduction of the thermal noise background, i.e. reducing the 300K thermal noise power of $P_{N} =kTRB$ at room temperature to the equivalent of 77K -the temperature of liquid nitrogen. We will present a detailed theoretical background which is needed to approach the expected gain in S/N for a spectrometer operated at temperatures significantly below the thermal environment.
Description
$^{g}$R.H. Dicke and R.W. Romer, Rev, Sci. Instrum. 26, 915(1955) $^{h}$J. Ekkers and W.H. Flygare, Rev. Sci. Instrum. 47, 448(1996). $^{i}$T.J. Balle and W.H. Flygare, Rev. Sci. Instrum. 52, 33(1981). $^{j}$J.U. Grabow and W. Stahl, Z. Naturforsch. 45a.1043(1990). $^{k}$J.U. Grabow, W. Stahl, and H. Dreizler, Rev. Sci. Instrum. 67, 4072(1996).
Author Institution: Radio and Geoastronomie Division Division of Engineering and Applied Sciences, Harvard-Smithsonion Center for Astrophysics Harvard University
Author Institution: Radio and Geoastronomie Division Division of Engineering and Applied Sciences, Harvard-Smithsonion Center for Astrophysics Harvard University