Abstract.
A method for high-precision pulsed photoacoustic spectroscopy applied to a simple system for detection of NO2 traces in nitrogen is presented. The acoustic signal from a closed cell containing NO2/N2 samples irradiated by a pulsed visible laser is analyzed in the frequency domain. A signal-processing method to obtain a high-resolution Fourier spectrum of the signal was developed. An accurate fitting of the resonance peaks with Lorentzian profiles gives high-precision determination of the amplitude and width of the resonance peaks. The resonance maximum is proportional to the absorbed energy; therefore, the choice of the laser wavelength, linewidth and frequency stability are critical for a precise calibration due to the fine structure of the NO2 optical spectrum. The method also allows high-accuracy measurement of the Q of the acoustic cavity. The dependence of Q on the buffer gas pressure is characteristic of an acoustic cavity where energy losses near the walls predominate. Consequently, an important enhancement of sensitivity takes place at high N2 pressure.
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Received: 1 June 2001 / Revised version: 27 July 2001 / Published online: 7 November 2001
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Slezak, V. High-precision pulsed photoacoustic spectroscopy in NO2-N2. Appl Phys B 73, 751–755 (2001). https://doi.org/10.1007/s003400100686
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DOI: https://doi.org/10.1007/s003400100686