Selective trace gas detection of complex molecules with a continuous wave optical parametric oscillator using a planar jet expansion

Abstract

The authors present a trace gas detection method for complex molecules using continuous cavity ring-down spectroscopy in combination with a continuous wave optical parametric oscillator (tunability wavelength: 2.8-4.8 mu m; power: 1 W) sampling a supersonic planar jet expansion (nozzle dimension: 3 cmx80 mu m). The improved molecular selectivity allows simultaneous detection of larger numbers of complex molecules. With a total optical path length of 180 m in the planar jet, a detection limit for methanol in an air expansion was determined at 70 ppbv, corresponding to a minimal detectable absorption of 2.2x10(-8) cm(-1) (over 90 s). (c) 2007 American Institute of Physics.