Abstract：Using a tunable near infrared external cavity diode laser and a 650mm long high finesse optical cavity consisting of two highly reflective (R＝99.97% at 6 561.39 cm-1) plan-concave mirrors of curvature radius ~1 000 mm, a cavity enhanced absorption spectroscopy (CEAS) system was made. The absorption spectra centered at 6 561.39 cm-1 of pure N2O gas and gas mixtures of N2O and N2 were recorded. According to the absorption of N2O at 6 561.39 cm-1 in the cavity, the measured effective absorption path was about 1 460 km. The spectra line intensity and line-width of N2O centered at 6 561.39 cm-1 were carefully studied. The relationship between the line-width of absorption spectra and the gas pressure was derived. The pressure broadening parameter of N2 gas for N2O line centered at 6 561.39 cm-1 was deduced and given a value of ~(0.114±0.004) cm-1·atm-1. The possibility to detect trace N2O gas in mixture using this CEAS system was investigated. By recording the absorption spectra of N2O gas mixtures at different concentration, the relationship between the line intensity and gas concentration was derived. The minimum detectable absorption was found to be 2.34×10-7 cm-1 using this cavity enhanced absorption spectroscopy system. And te measurement precision in terms of relative standard deviation (RSD) for N2O is ~1.73%, indicating the possibility of using the cavity enhanced absorption spectroscopy system for micro gas N2O analysis in the future.
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