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Author: search.filters.author.Keeratirawee, KanchalarSubject: search.filters.subject.Photoacoustic spectroscopy

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    Piezoelectric tube as resonant transducer for gas-phase photoacoustics
    (2021-02-22)
    Keeratirawee, Kanchalar
    ;
    Hauser, Peter C.
    The use of a piezoelectric tube for the photoacoustic gas-phase determination of NO<inf>2</inf> as a model analyte is demonstrated. The tube is made from lead zirconate titanate with 30 mm length and 5.35 mm internal diameter. Its inner and outer surfaces are coated with electrodes. The tube serves as both, resonance body and transducer. The design is thus simpler than the usual combination of resonance tube and microphone as the two functions are embodied in the same component. The main resonance frequency of the tube was found to be 5341 Hz. A blue laser diode emitting at 450 nm was employed as light source for the determination of NO<inf>2</inf>. The limit of detection was determined as 83 ppbV and the calibration curve was linear with a coefficient of determination (r<sup>2</sup>) of 0.9998 up to the highest concentration of 15 ppmV tested.
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    Photoacoustic detection of ozone with a red laser diode
    (2021-02-01)
    Keeratirawee, Kanchalar
    ;
    Hauser, Peter C.
    The photoacoustic detection of ozone using the Chappuis band is demonstrated. A visible red laser diode emitting at 638 nm was employed as a light source. The photoacoustic cell consisted of a conventional resonance tube with a MEMS (microelectromechanical systems) microphone placed outside an opening along the tube. A calibration curve for the range from 33 ppmV to 215 ppmV was found to be highly linear with a coefficient of determination (r<sup>2</sup>) of 0.9999, when allowing for different measurement frequencies to account for shifts in the speed of sound due to changes in the gas matrix. The limit of detection was found to be 1.6 ppmV for an optical power of the laser diode of about 130 mW.