Tunable diode laser measurement of nitrous oxide in air

Abstract

Infrared derivative spectroscopy using a tunable diode laser coupled to a multipass absorption cell has been used to measure the nitrous oxide mole fraction in tropospheric air samples. The individual measurement precision was 1.5% (1σ). No temporal variation outside the statistical error limits was observed in 26 measurements over a two month period. Absolute values were obtained by comparison to manometrically calibrated standards prepared by static dilutions of N 2 O in air to ambient levels. The mean mole fraction of N 2 O in dry air was determined to be 298±5 ppb where the error includes an estimate of possible systematic errors in standard preparation.