Synchrotron X-Ray Diffraction Studies of Phase Transitions in Physisorbed Monolayers of Rare Gases on Graphite

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    This study is an investigation of phase transition in monoatomic layers adsorbed on graphite. Such effects can be considered physical realizations of two-dimensional systems. The experimental technique used is synchrotron X-ray diffraction. A scattering geometry which utilizes a position-sensitive detector is developed and used for the experimental studies discussed below and carried out at the DORIS storage ring at Deutsches Elektronen-Synchrotron (DESY), Hamburg, Germany. Systems which have been investigated include the commensurate-incommensurate phase transition in krypton monolayer. By adjusting the spreading pressure in the krypton layer by means of a coadsorbent deuterium gas it has been unambiguously demonstrated that at low temperatures the phase transition is of first order. A melting study of incommmensurate argon monolayers demonstrates an experimental verification of the possibility for having a continuous melting transition in two-dimensions. Mixtures of two-components have been investigated for their phases. No (chemical) order-disorder transition is seen. A discussion is given on this lack ot a chemical order. This lack is utilized to study the commensurate-incommensurate phase transition driven by average particle size. Finally, a special low-temperature phase is identified in a xenon monolayer which is diluted with freon.
    Original languageEnglish
    Place of PublicationRoskilde
    PublisherRisø National Laboratory
    Number of pages135
    ISBN (Print)87-550-1014-8
    Publication statusPublished - 1984
    SeriesDenmark. Forskningscenter Risoe. Risoe-R


    • Risø-R-504
    • Risø-R-504(EN)

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