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Methane concentration and isotopic composition measurements with a mid-infrared quantum-cascade laserA quantum-cascade laser operating at a wavelength of 8.1 micrometers was used for high-sensitivity absorption spectroscopy of methane (CH4). The laser frequency was continuously scanned with current over more than 3 cm-1, and absorption spectra of the CH4 nu 4 P branch were recorded. The measured laser linewidth was 50 MHz. A CH4 concentration of 15.6 parts in 10(6) ( ppm) in 50 Torr of air was measured in a 43-cm path length with +/- 0.5-ppm accuracy when the signal was averaged over 400 scans. The minimum detectable absorption in such direct absorption measurements is estimated to be 1.1 x 10(-4). The content of 13CH4 and CH3D species in a CH4 sample was determined.
Document ID
20040088906
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Kosterev, A. A.
(Rice Quantum Institute, Rice University Houston, Texas 77251-1892, United States)
Curl, R. F.
Tittel, F. K.
Gmachl, C.
Capasso, F.
Sivco, D. L.
Baillargeon, J. N.
Hutchinson, A. L.
Cho, A. Y.
Date Acquired
August 21, 2013
Publication Date
December 1, 1999
Publication Information
Publication: Optics letters
Volume: 24
Issue: 23
ISSN: 0146-9592
Subject Category
Meteorology And Climatology
Funding Number(s)
CONTRACT_GRANT: DAA G 55-98-C-0050
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
NASA Discipline Environmental Health

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