We have developed a portable photoacoustic spectrometer that offers routine, precise and accurate measurements of atmospheric carbon dioxide mixing ratios. The spectrometer is temperature controlled, continuously samples and dries atmospheric air, and employs an intensity-modulated distributed feedback laser and fiber amplifier operating near 1.57 µm. For measurements of carbon dioxide mixing ratio in air, we demonstrate a measurement precision (60 s averaging time) of 0.15 µmol mol-1 and achieve a standard uncertainty of 0.8 mol mol-1 by calibrating the analyzer response in terms of certified gas mixtures. We also investigate how water vapor affects the photo-acoustic signal by promoting collisional relaxation of the carbon dioxide.
Applied Physics B
photoacoustic, carbon dioxide, greenhouse gas