Analysis of the Causes of the Inverse Population of Atomic Argon Levels in Condensing Supersonic Flows of Mixtures

Abstract

The features of argon radiation mixed with molecular and atomic additives in condensing supersonic jets are analyzed. Mixtures of argon (95%) with methane (5%) and argon (95%) with monosilane (5%) are used. The mixture’s particles are activated by a well-focused electron beam. The dependence of the radiation intensity of individual argon lines on the gas-dynamic parameters in the jet is studied. In a certain pressure range, different various compositions of mixtures, not only anomalously intense emission was recorded on individual spectral lines of argon (Ar_I) in mixtures with methane and monosilane, but also the role of clusters of a certain size and composition was revealed. At the same time, a similar effect is not detected in the spectrum of argon (Ar_II) ions. It is established that the cause of the anomaly is a highly efficient molecular cluster mechanism of the selective excitation of the individual levels of argon atoms, which is absent in noncondensing jets and weakens at the stage of the formation of large clusters. The main channels of energy transmission are reviewed and discussed. Based on the data obtained, an empirical model of the excitation-emission process is proposed.