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TT: Tiefe Temperaturen

TT 7: Superconductivity & Solids At Low Temperature - Poster Session

TT 7.73: Poster

Montag, 27. März 2006, 14:00–17:45, P1

Electron diffraction study of clusters formed in a supersonic jet of Ar-Kr gas mixture — •Oleksandr Danylchenko, Spartak Kovalenko, and Vladimir Samovarov — B. Verkin Institute for Low Temperature Physics and Engineering of the NASU, 47, Lenin Ave., 61103 Kharkiv, Ukraine

Rare-gas clusters, characterized by a relatively simple character of the atomic interaction forces, are convenient model objects for testing various theoretical scenarios that describe mechanisms and velocities of formation of various physical properties in macrosystems. Rare-gas clusters also can serve as a model system for the metallic clusters, which are important from the viewpoint of their application. A large amount of papers are dedicated to the study of the structure of pure rare gases. At the same time, multicomponent clusters are much less studied so far. Here we study the structure and nucleation of clusters formed in an adiabatically expanding gas mixture Ar-Kr by electron diffraction. We found that small admixtures of Kr (1000 and 5000 ppm) cause an essential increase in Ar cluster size. This effect is due to the substitution of the heterogeneous clusterization for the homogeneous one. In this case, core aggregations are composed mainly of Kr atoms. This result correlates well with the data of optical measurements. It is also shown that at great concentrations of Kr (200000 ppm) only Kr clusters are formed. Argon is a carrying gas and favors temperature lowering in the Kr aggregations. We demonstrate that in large crystalline clusters (10^4-10^5 atoms per cluster) an hcp structure is realized. We discuss possible processes responsible for the formation of the hcp structure.