Lipid and Simple Liquid Surfaces

Jens Aage Als-Nielsen

    Research output: Contribution to journalJournal articleResearch

    Abstract

    X-ray reflectivity of a liquid surface at glancing angles α well beyond the glancing angle αC for total reflection yields detailed information about the average electron density profile ρ(z) across the surface. It is easily shown1 that the ratio of the observed reflectivity R(α) and the Fresnel reflectivity RF(α) corresponding to an infinitely sharp density profile measures the Fourier transform of the density gradient ρ'(z) : R(α)/RF(α) = |∫ρ'(z)exp(iQz) dz|2 with Q = 2ksinα being the wave vector transfer at specular reflection. The method has been used to investigate (i) thermal roughness of simple liquids2 (ii) smectic layering of liquid crystals3,4,5 (iii) monolayers on water of fatty acids6, surfactants7, phospholipids8 and of microemulsions9 Using thermal neutrons beams in stead of X-rays one can enhance the contrast between monolayer and subphase and of specific parts of molecules by isotope substitution10. Neutron reflectivity is also sensitive to surface magnetism. In-plane structures6,7,8 can be deduced from grazing incidence diffraction for α near αC.
    Original languageEnglish
    JournalJournal de physique. Colloque
    Volume50
    Issue numberC7
    Pages (from-to)21-22
    ISSN0449-1947
    DOIs
    Publication statusPublished - 1989

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