Ammonia and ethene absorption measurements with a tunable CO{sub}2 laser-based photoacoustic trace gas detector

摘要

During the last years, the development of optical spectroscopic techniques have made possible measurements of weak IR absorption lines of many gases with biological, agricultural and environmental interest. An extracavity configuration for trace gas detection, based on CO{sub}2 laser photoacoustic (PA) spectroscopy is discussed. We show the use of this system to determine the absorption spectra of ammonia (NH{sub}3) and ethene (C{sub}2H{sub}4) for diluted absorber-nitrogen mixtures of 13 ppm at 54 different CO{sub}2 laser wavelengths (between 9 and 11 μm). Due to specific features of the experimental systems, the results reported in literature present significant differences for some important spectral lines. The measurements were performed at room temperature (300K) and atmospheric pressure. In addition, the detection limits of C{sub}2H{sub}4, NH{sub}3 and O{sub}3 were calculated.