8 ITMP3 / 8éme conférence internationale de photoacoustique et photothermique
J. Phys. IV France 04 (1994) C7-499-C7-502
Spectrally resolved detection of NH3 at ppb levelJ. Henningsen1, T. Møgelberg1 and M. Hammerich2
1 Danish Institute of Fundamental Metrology, Bldg. 307, Lundtoftevej 100, 2800 Lyngby, Denmark
2 Rungsted Gymnasium, Stadion Alle 14, 2960 Rungsted Kyst, Denmark
Photoacoustic detection of 30 ppb ammonia in air is demonstrated with a signal to noise ratio of 40, using a 400 MHz tunable CO2 laser as radiation source. Interference from CO2 is controlled by monitoring near the Doppler limit and by using phase information to separate the two signals. Wall adhesion is studied quantitatively. It is shown that the walls constitute a reservoir of fixed size, which is filled up at a rate proportional to the NH3 concentration.
© EDP Sciences 1994