J. Phys. IV France 125 (2005) 7-10
Methane monitoring by near infrared photoacoustic spectroscopy: The importance of relaxation phenomenaS. Schilt1, J.-Ph. Besson2 and L. Thévenaz1
1 Nanophotonics and Metrology Laboratory, Swiss Federal Institute of Technology, 1015 Lausanne, Switzerland
2 Nanophotonics and Metrology Laboratory, Swiss Federal Institute of Technology, 1015 Lausanne, Switzerland
The importance of molecular relaxation in photoacoustic spectroscopy is discussed. The particular case of methane monitoring in dry oxygen using a 1.65-m laser-based photoacoustic sensor is reported. The slow vibration-to-translation energy transfer occurring in this gas mixture results in a drastic reduction of the detection sensitivity. A quadratic response of the sensor to the methane concentration is also reported and explained by molecular relaxation effects.
© EDP Sciences 2005