Mobile laser spectrometer with novel resonant multipass photoacoustic cellfor trace-gas sensing

The development and application of a mobile laser-photoacoustic spectromete r for in situ multicomponent monitoring of trace gases in different environ ments is reported. Sub-ppbV (< 10(-9) per volume)-concentrations can be mea sured with a novel resonant multipass photoacoustic cell. The cell is desig ned for flow mode operation in order to reduce adsorption effects. For ethe ne (C2H4) buffered in synthetic air a minimum detection limit of 70 ppt V ( 70 x 10(-12) per volume) is achieved corresponding to a minimum measurable absorption coefficient alpha(min) = 2 x 10(-9) cm(-1) for a signal-to-noise ratio of 3. The multicomponent capability of the system is demonstrated wi th continuous sequential measurements of ethene, methanol, ethanol, CO2, an d H2O of air from a fruit storage chamber.