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Fast Response tunable diode laser spectroscopy for trace gas flux measurements

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Fast Response tunable diode laser spectroscopy for trace gas flux measurements

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Title: Fast Response tunable diode laser spectroscopy for trace gas flux measurements
Author: Wienhold, F.G.; Fischer, H.; Harris, G.W.
Abstract: A fast tunable diode laser spectrometer was applied for measurements of N2O emissions from a harvested wheat field located in Sealand, Denmark. The dual-channel instrument uses two tone frequency modulation and signal detection at 11 MHz in conjunction with rapid (1 ms) scanning of the laser. A dichroic beam combiner and a mechanical chopper allow time multiplexing. The absorption signals are recorded and analysed on-line. The combination of a software, current and temperature controlled line locking scheme results in high stability of the instrument. The time response (200 ms) of the spectrometer is limited by the measurement-cell gas exchange. For eddy correlation measurements, the trace gas mixing ratio and wind data were sampled synchronously at a rate of 10 Hz using an interrupt-driven algorithm. Mean N2O flux detection limits were 6 pptv m s−, corresponding to a deposition velocity of 2 × 10−5 m s− for a half hour measurement time. In addition, concentration gradients were determined from measurements at four different inlet heights at 0.1 ppbv precision in a shared integration time of 30 min. These measurements resulted in a flux detection limit of 7 pptv m s−1 ror the boundary layer mixing conditions encountered.
Type: Article
Rights: http://www.elsevier.com/wps/find/journaldescription.cws_home/525439/description#description
URI: http://hdl.handle.net/10315/4205
Published: Elsevier
Citation: Infrared Physics and Technol., 37, 67-74.
Date: 1996

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