External cavity diode laser based photoacoustic detection of CO2 at 1.43 microm: the effect of molecular relaxation.
Photoacoustic spectroscopy, based on an external cavity diode laser operating at 1431 nm, was used for measuring CO2 concentration as a minority component in a gas mixture. By using N2 as a buffer gas, a molecular relaxation effect was observed, which influenced both the amplitude and the phase of the measured photoacoustic signal and consequently reduced the sensitivity of the PA system. This molecular relaxation effect could be suppressed by adding water vapor of a constant and relatively high (approximately 4%) concentration to the gas sample. In parallel with this, the arising spectral interference between H2O and CO2 necessitated the development of a simple yet efficient signal analysis method, which increased the sensitivity of the system by more than one order of magnitude and accordingly reduced the minimum detectable CO2 concentration down to approximately 1000 ppm.
Veres
Anikó
A
Department of Optics and Quantum Electronics, University of Szeged, H-6701 Pf 406 Szeged, Hungary.
Bozóki
Zoltán
Z
Mohácsi
Arpád
A
Szakáll
Miklós
M
Szabó
Gábor
G
D000162:Acoustics; D002245:Carbon Dioxide / Q000032:analysis*; D007834:Lasers; D012680:Sensitivity and Specificity; D019265:Spectroscopy, Near-Infrared / Q000295:instrumentation*; D013816:Thermodynamics
D002245:Carbon Dioxide