Cavity ring-down spectroscopy for trace gas analysis

Cavity Ring-Down Spectroscopy (CRDS) is a novel technique of measurement of the absorption coefficient based on determination of the Q-factor of an optical resonator which contains the investigated absorber. We present a modified CRDS method (so called CRD-Spectrography) in which the signal is simultaneously analysed within a broad spectral range. This technique was used for monitoring of trace gases (nitrogen oxides) in the atmosphere. Another modification of CRDS technique allows to determine the transient absorption coefficient. This method was applied for studies of kinetics of CH radical produced by pulsed electric discharge in methane.