ISSTT Proceedings

ISSTT Proceedings

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In situ Quantitative THz Gas Analysis

Authors:
John C. Pearson, Brian J. Drouin, Ken B. Cooper, Robert A. Stachnik
Abstract:
The rotational spectrum of gas phase molecules offers the potential to be an extremely powerful tool for analytical chemistry. Every polar molecule features a unique rotational spectrum with a band origin at DC. The resolution of phase locked microwave techniques can easily be 1 part in 1010 while the Doppler limited line widths are one part in 106. In the absence of significant optical depth the intensities of Doppler limited lines are linearly proportional to the total column. For insitu applications a microwave source illuminates the gas and power is measured as a function of frequency allowing the comparatively narrow lines to be detected even when there is significant gain or power structure. The illuminating source can easily have a brightness temperature greater than 1014K so that extremely weak features can be detected. The result is that rotational techniques facilitate extremely sensitive chemical identification and have the potential for very accurate total abundance determination. The development and calibration of ambient temperature in situ rotational spectroscopic systems operating between 0.1 and 0.6 THz for planetary science is presented. Optimization of this type of system requires some rather different considerations than are typical for space based remote sensing instruments. The system considerations, the calibration and potential applications of in situ spectroscopy are discussed.
Categories:
Applications, Components
Year:
2009
Session:
T4
Full-text:
Download a PDF of this paper.
Page Number(s):
120-127