Diode laser spectrometer for monitoring up to five atmospheric trace gases in unattended operation.

An automated diode laser spectrometer for recording concentrations of trace gases is described. It has been tested for unattended operation in the laboratory and at an atmospheric surveillance station for several months. The sensitivities reached are, e. g., 50 ppt for NO2 and 300 ppt for NO. In an optical path length of 100 m the lowest extinction measured in unattended operation is about 1.5 x 10 exponent -5 for a measuring time of about 60 s. Recording of trace gases are shown for urban and rural atmospheric conditions.