Authors: N Barreiro A Peuriot G Santiago V Slezak
Publish Date: 2012/04/27
Volume: 108, Issue: 2, Pages: 369-375
Abstract
Photoacoustic spectroscopy is widely applied for tracegas detection because of its sensitivity and low detection limit In a previous work where we studied the potential application to methane monitoring under a resonant excitation at 33 μm we showed that the signal from methane–nitrogen mixtures decreases with the addition of oxygen This effect is due to an energy exchange between the ν 4 asymmetric stretching mode of methane and the first metastable level of oxygen This process makes oxygen accumulate energy thus hindering the generation of the photoacoustic signal In this work we study the possible addition of water as a good collisional partner of oxygen in order to obtain a greater sensitivity We develop a model based on rate equations and find good agreement between theory and measurements The experiment is carried out with a novel cell of rectangular cross section and a Q factor of 165±1 We find that 07 water content is large enough to obtain a signal as high as in the methane–nitrogen case at atmospheric pressure
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