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- Title
New method for isotopic ratio measurements of atmospheric carbon dioxide using a 4.3 μm pulsed quantum cascade laser.
- Authors
Nelson, D. D.; McManus, J. B.; Herndon, S. C.; Zahniser, M. S.; Tuzson, B.; Emmenegger, L.
- Abstract
We present a new approach to the measurement of stable isotopic ratios of carbon dioxide using a near-room-temperature pulsed quantum cascade laser and a spectral ratio method based upon dual multiple pass absorption cells. The spectral ratio method improves precision and accuracy by reducing sensitivity to variations in the laser tuning rate, power and line width. The laser is scanned across three spectral lines (near 2310 cm-1) quantifying three CO2 isotopologues: 12C16O2, 13C16O2 and 12C16O18O. Isotopic ratios are determined simultaneously with a precision of 0.2δ for each ratio with a one-second measurement. Signal averaging for 400 s improves the precision to better than 0.03δ for both isotopic ratios (13 R and 18 R). Long-term accuracy of 0.2 to 0.3δ is demonstrated with replicate measurements of the same sample over a one-month period. The fast time response of this instrument is suitable for eddy flux measurements.
- Subjects
CARBON dioxide; ATMOSPHERIC chemistry; ATMOSPHERIC carbon dioxide; PHYSICAL &; theoretical chemistry; MODULATION spectroscopy; SPECTRUM analysis
- Publication
Applied Physics B: Lasers & Optics, 2008, Vol 90, Issue 2, p301
- ISSN
0946-2171
- Publication type
Article
- DOI
10.1007/s00340-007-2894-1