Ethylene monitoring by differential absorption with a CO₂ waveguide laser

Abstract

In this paper we report on a differential absorption technique using a CO₂ waveguide laser. The method is based on the measurement of the differential absorption between two different frequencies of the same selected CO₂ laser line. The sensitivity of the technique depends strongly on the total pressure and has been estimated to be about a few tens of ppb or better over a 1 km path length in C₂H₄ diluted with air to a total pressure of a few tens of torrs. Its relative simplicity and high sensitivity at low total pressure enable this technique to be applied to gas detection either at high altitude or to local monitoring of a low pressure sample.