TITLE

Standard photoacoustic spectrometer: Model and validation using O2 A-band spectra

AUTHOR(S)
Gillis, K. A.; Havey, D. K.; Hodges, J. T.
PUB. DATE
June 2010
SOURCE
Review of Scientific Instruments;Jun2010, Vol. 81 Issue 6, p064902
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
We model and measure the absolute response of an intensity-modulated photoacoustic spectrometer comprising a 10 cm long resonator and having a Q-factor of approximately 30. We present a detailed theoretical analysis of the system and predict its response as a function of gas properties, resonance frequency, and sample energy transfer relaxation rates. We use a low-power continuous wave laser to probe O2 A-band absorption transitions using atmospheric, humidified air as the sample gas to calibrate the system. This approach provides a convenient and well-characterized method for calibrating the absolute response of the system provided that water-vapor-mediated relaxation effects are properly taken into account. We show that for photoacoustic spectroscopy (PAS) of the O2 A-band, the maximum conversion efficiency of absorbed photon energy to acoustic energy is approximately 40% and is limited by finite collision-induced relaxation rates between the two lowest-lying excited electronic states of O2. PAS also shows great potential for high-resolution line shape measurements: calculated and experimental values for the PAS system response differ by about 1%.
ACCESSION #
51848898

 

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