Browsing by Author "Gog, T"

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    Adsorption at liquid interfaces: a comparison of multiple experimental techniques
    (EDP Sciences, 2009-02) Law, BM; Brown, MD; Marchand, L; Lurio, LB; Hamilton, WA; Kuzmenko, I; Gog, T; Satija, S; Watkins, E; Majewski, J
    It has proven to be a challenging task to quantitatively resolve the interfacial pro. le at diffuse interfaces, such as, the adsorption pro. le near a bulk binary liquid mixture critical point. In this contribution we examine the advantages and disadvantages of a variety of experimental techniques for studying adsorption, including neutron reflectometry, X-ray reflectometry and ellipsometry. Short length scale interfacial features are best resolved using neutron/X-ray reflectometry, whereas, large length scale interfacial features are best resolved using ellipsometry, or in special circumstances, neutron reflectometry. The use of multiple techniques severely limits the shape of the adsorption pro. le that can describe all experimental data sets. Complex interfaces possessing surface features on many different length scales are therefore best studied using a combination of neutron/X-ray reflectometry and ellipsometry. © 2009, EDP Sciences
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    X-ray and ellipsometric study of strong critical adsorption
    (American Physical Society, 2007-06) Brown, MD; Law, BM; Marchand, L; Lurio, LB; Kuzmenko, I; Gog, T; Hamilton, WA
    Carpenter [Phys. Rev. E 61, 532 (2000)] succeeded in determining a single universal model, called the P1 model, that could describe the ellipsometric critical adsorption data from the liquid-vapor interface of four different critical binary liquid mixtures near their critical demixing temperatures. The P1 model also recently has been used to describe neutron reflectometry data from a critical liquid mixture/crystalline quartz interface. However, in another recent study, the P1 model failed to simultaneously describe x-ray reflectometry and ellipsometry data from the liquid-vapor surface of the critical mixture n-dodecane + tetrabromoethane (DT). In this paper, we resolve this discrepancy between x-ray and ellipsometric data for the DT system. At large length scales (far from the interface) the local concentration is described by the P1 model in order to correctly reproduce the temperature dependence of the ellipsometric data. Close to the interface, however, the molecular structure must be correctly accounted for in order to quantitatively explain the x-ray data. An important conclusion that arises from this study is that neutron or x-ray reflectometry is most sensitive to short-range interfacial structure, but may provide misleading information about long-range interfacial structure. Ellipsometry provides a more accurate measure of this long-range interfacial structure. Complex interfacial structures, possessing both short- and long-range structure, are therefore best studied using multiple techniques. © 2007, American Physical Society