Size and composition of clusters produced by supersonic expansion of binary gas mixtures

TL;DR

This study investigates the size and composition of clusters formed by supersonic expansion of binary gas mixtures, revealing how cluster composition differs from the initial mixture and depends on size, with theoretical models supporting the findings.

Contribution

It introduces a quantitative analysis of cluster composition based on critical radius and component concentration, applicable to various van der Waals systems.

Findings

Cluster compositions differ significantly from initial mixtures.

Critical radius and component concentration determine cluster enrichment.

Theoretical models accurately describe experimental results.

Abstract

Size and composition of clusters produced by adiabatic expansion of binary gas mixtures (Ar-Kr, Kr-Xe, and N2-Ar) with various component concentrations are studied by using electron-diffraction technique. The resulting homogeneous and heterogeneous clusters are shown to have compositions substantially different from those of the primary gas mixtures and dependent on cluster size. We have found that the key parameters needed for an analysis of cluster composition are the critical cluster radius and the heavier component concentration in the gas mixture that can be used to establish the regions of existence of homogeneous and heterogeneous clusters. These critical values determine the coefficient of the enrichment of clusters with the heavier component with respect to its concentration in the primary gas mixture. Theoretical relations are obtained which provide a good quantitative description of the experimental results and can be expected to be also valid for finding the composition of binary clusters of other van der Waals systems.