title: Imaging critical fluctuations of pure fluids and binary mixtures.
abstract: We use optical microscopy techniques to directly visualize the structures that emerge in binary mixtures and pure fluids near their respective critical points. We attempt to understand these structures by studying the image formation using both a phase contrast and a dark field filter to our microscope. We found that images of critical fluctuations for both liquid-liquid and liquid-gas critical systems have gray level intensity histograms with Gaussian shape. For all fluids investigated, the temperature-dependent standard deviation of the Gaussian histogram follows a power law with the same exponent. Since the image intensity fluctuations are determined by order parameter fluctuations, this direct imaging method allowed us to estimate the critical exponent of compressibility with very good accuracy.
authors.affiliation: Department of Physics, University of New Orleans, New Orleans, Louisiana 70148, USA.
authors.forename: John J
authors.initials: JJ
authors.lastname: Hegseth
authors.affiliation: Department of Physics and Astronomy, College of Charleston, Charleston, South Carolina 29424, USA.
authors.forename: Ana
authors.initials: A
authors.lastname: Oprisan
authors.affiliation: ESEME, Institut de Chimie de la Matière Condensée de Bordeaux, UPR 9048, CNRS, Université de Bordeaux I, Avenue du Dr. Schweitzer, F-33608 Pessac Cedex, France.
authors.forename: Yves
authors.initials: Y
authors.lastname: Garrabos
authors.affiliation: Physique et Mécanique des Milieux Hétérogènes, UMR 7636 CNRS - ESPCI - Université Pierre et Marie Curie - Université Paris Diderot, 10 rue Vauquelin, 75005 Paris, France and Service des Basses Températures, CEA-Grenoble & Université Joseph Fourier, Grenoble, France.
authors.forename: Daniel
authors.initials: D
authors.lastname: Beysens
mesh_terms: D005740:Gases; D058610:Isobutyrates; D008858:Microscopy, Phase-Contrast / Q000379:methods*; D061848:Optical Imaging / Q000379:methods*; D044366:Transition Temperature; D014867:Water
chemical_list: D005740:Gases; D058610:Isobutyrates; D014867:Water; C020380:isobutyric acid