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[18.18] Absorption Spectra for the 889 nm Band of Methane derived from Intracavity Laser Spectroscopy Measurements made as a Function of Low Sample Temperatures

J. J. O'Brien, S. Shaji (University of Missouri-St. Louis)

Special intracavity laser, cryogenically-operable absorption cells will be described. The cell that enables spectra to be acquired for methane temperatures between 77 and 150 K consists of four concentric cylindrical compartments (vacuum envelope, cryogenic compartment, helium-gas chamber, methane chamber). The inclusion of the helium gas containing chamber between the methane chamber and the cryogenic chamber and a series of temperature sensors are to ensure good temperature monitoring and control. Absorption spectra of methane in the 889 nm band have been recorded with these cells using a broadband intracavity laser spectroscopy technique. Spectra are recorded at high spectral resolution for a series of narrow, overlapping spectral regions at methane temperatures down to 77 K. Methane absorption coefficients are derived from these measurements, following deconvolution of the spectra for the instrument function.

Support from NASA's Planetary Atmospheres Program under grant number NAG5-12013 is gratefully acknowledged.

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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.