Simultaneous detection of ammonia, methane and ethylene at 1.63 μm with diode laser photoacoustic spectroscopy

Spectral investigation around 6115 cm^-1 for simultaneous detection of ammonia, methane and ethylene in gas samples is presented. Experimental data on the ν₂+ν₃+ν₄ combination band of ammonia are reported with a resolution of 1.5 GHz. A trace gas analyzer based on a resonant photoacoustic cell and an external cavity diode laser has been used for detection. A data fitting procedure has been developed in order to improve the system sensitivity and to limit the need of a reference cell. The selected spectral region allows a sensitivity of about 60 ppm for ammonia, 6 ppm for methane and 30 ppm for ethylene with 0.3 mW laser power. An application of simultaneous detection of such molecules in a mixture reproducing their typical abundances in real gas samples from biomass gasification is discussed. PACS 42.62.Fi; 42.55.Px; 82.80.Ch