DE3929079

In a procedure for analysing gaseous media, in particular for determining the concentration of a gas in a gas mixture, by means of microwave spectroscopy, the microwave radiation is coupled in pulsed form into a resonator which can be tuned to different frequencies and which is situated in an evacuated receiving vessel. The gas mixture to be examined is admitted as a pulsed molecular beam into the receiving vessel using air as carrier gas. The mixed state formed by the microwave pulse produces an emission which, during the intervals in the incident microwave pulses, is coupled out from the resonator into a receiving unit. After down-conversion to frequencies preferably in the region below 50 MHz, the test signal is digitised and evaluated, during which process a Fourier analysis may be carried out.