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Impact of water vapor on 1.51 μm ammonia absorption features used in trace gas sensing applications
Auteur(s)
Date de parution
2010
In
Applied Physics B : Lasers and Optics, Springer, 2010/100/2/349-359
Résumé
Water-vapor-induced pressure broadening is reported for two NH<sub>3</sub> absorption features at 6612.7 and 6596.4 cm<sup>−1</sup> that are exploitable for gas sensing applications at atmospheric pressure. Absorption spectra of different NH<sub>3</sub>–H<sub>2</sub>O–N<sub>2</sub> mixtures were measured at an elevated temperature of 70°C to enable high H<sub>2</sub>O concentrations to be reached. Line parameters were determined from a fitting procedure. The significantly greater values obtained for the H2O-broadening coefficients of the two lines compared to N<sub>2</sub>-broadening leads to cross-sensitivity effects in NH3 trace gas sensors based on spectroscopic techniques that are sensitive to the width of the analyzed absorption line, as is the case in a simple implementation of wavelength modulation spectroscopy or in photoacoustic spectroscopy. In such a case, cross-sensitivity results in inaccurate gas concentration retrieval when the composition of the diluting gas changes. H2O represents a potentially significant cross-sensitivity source as its concentration may be subject to large variations, especially in high-temperature applications where concentrations up to a couple of tens of percent may be encountered. In contrast to interference which can be minimized by an appropriate choice of the analyzed transitions, cross-sensitivity affects the entire spectrum of the analyte and is thus unavoidable in the mentioned type of gas sensors.
Identifiants
Type de publication
journal article
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