Electron diffraction study of the formation and growth of clusters in supersonic binary N2-Kr gas jets

Abstract

An electron diffraction diagnostics of substrate-free clusters formed in N2-Kr binary jets expanding through a supersonic nozzle into vacuum was carried out. Gas mixtures contained 0.5, 1, and 6 mol.% krypton, the measured average sizes of aggregations in the cluster beam varied from 500 to 30,000 molecules per cluster. A change in the nucleation mechanism in the jet from heterogeneous to homogeneous was revealed when the temperature of the gas mixture at the nozzle inlet T0 increased from 100 K to 120 K, which had a profound effect on the sizes, phase composition and component composition of the clusters. It was established that the intensification of cluster growth by inserted krypton nucleation centers at T0 = 100 K occurs through an increase in the fraction of the fcc phase. At T0 = 120 K, the effect of cluster growth suppression by the addition of an impurity with significantly stronger intermolecular forces was revealed for the first time. It is shown that the effect is manifested when the krypton gas content increases to 6 mol.% and is caused by the kinetics of gas condensation in a supersonic jet.