This paper seeks to substantiate the use of the electron-induced fluorescent (electron-beam) technique for measuring the densities of gas components in mixtures of N2O, O-2, Ar, and SiH4 over the range 10(13)less than or equal to 10(17) cm(-3). Experiments have been carried out in free jets which are a convenient gas target far investigations of this kind. Several strong spectrally resolved electron-induced emissions in these gases have been chosen. It is shown that radiating states are excited by direct electron impact. The rate constants of collisional quenching of fluorescence have been measured, which made it possible to expand the field of application of the method. A method is proposed, and an experiment has been carried out to measure the absolute concentration of mixture components in a real plasma-chemical reactor.