| Author(s): |
Keith A. Gillis; Daniel K. Havey; Joseph T. Hodges; |
| Title: |
Standard Photoacoustic Spectrometer: Model and Validation using O2 A-Band Spectra |
| Published: |
June 30, 2010 |
| 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. The technique also shows great potential for high-resolution line shape measurements. We directly compare calculated and experimental values for the PAS system response and show that they differ by about 1%. |
| Citation: |
Review of Scientific Instruments |
| Volume: |
81 |
| Pages: |
pp. 064902-1 - 064902-13 |
| Keywords: |
A-band; aerosol; calibration; line shape; molecular relaxation; oxygen; photoacoustic spectrometry; water |
| Research Areas: |
Measurement Standards, Climate Science Measurements, Gas Metrology, Standards, Chemical Engineering & Processing, Chemistry, Metrology, Aerosol/Particulate Measurements and Standards, Spectroscopy |
| PDF version: |
 Click here to retrieve PDF version of paper (593KB) |
