title: Ammonia detection by using quantum-cascade laser photoacoustic spectroscopy.
abstract: A pulsed quantum-cascade distributed-feedback laser, temperature tunable from -41 degrees C to +31.6 degrees C, and a resonant differential photoacoustic detector are used to measure trace-gas concentrations to as low as 66 parts per 10(9) by volume (ppbv) ammonia at a low laser power of 2 mW. Good agreement between the experimental spectrum and the simulated HITRAN spectrum of NH3 is found in the spectral range between 1046 and 1052 cm(-1). A detection limit of 30 ppbv ammonia at a signal-to-noise ratio of 1 was obtained with the quantum-cascade laser (QCL) photoacoustic (PA) setup. Concentration changes of approximately 50 ppbv were detectable with this compact and versatile QCL-based PA detection system. The performance of the PA detector, characterized by the product of the incident laser power and the minimum detectable absorption coefficient, was 4.7 x 10-9 W cm(-1).
authors.affiliation: Laboratório de Ciências Físicas, Centro de Ciência e Technologia, Universidade Estadual do Norte Fluminense, Campos dos Goytacazes-RJ, Brazil.
authors.forename: Milton B
authors.initials: MB
authors.lastname: Filho
authors.forename: Marcelo G
authors.initials: MG
authors.lastname: da Silva
authors.forename: Marcelo S
authors.initials: MS
authors.lastname: Sthel
authors.forename: Delson U
authors.initials: DU
authors.lastname: Schramm
authors.forename: Helion
authors.initials: H
authors.lastname: Vargas
authors.forename: Andras
authors.initials: A
authors.lastname: Miklós
authors.forename: Peter
authors.initials: P
authors.lastname: Hess