Investigation on infrared laser absorption spectroscopy measurement of acetylene trace quantities

A laser-based infrared spectrometer was developed for use in high-resolutio n spectroscopic analysis of trace gases in the atmosphere. Continuous wave, broadly tunable coherent infrared radiation was generated from 8 to 19 mum in a gallium selenide crystal by laser difference-frequency mixing. Measur ements of acetylene trace concentrations using laser absorption spectroscop y are reported. The measurements have been performed by using the P(21), Q( 11), and R(9) lines of the v(5) band, respectively, in order to investigate optimal detection conditions: a trade-off choice between higher line absor ption strength for sensitive detection and better spectral discrimination f rom lines overlapping for open path trace-gas monitoring applications. Mini mum detectable concentrations are compared under different experimental con ditions. The v(5) R(9) line seems to be close to optimum in terms of absorp tion strength and freedom from spectral interference for spectroscopic dete ction of acetylene trace concentration at atmospheric pressure. (C) 2000 El sevier Science B.V. All rights reserved.