Near-critical light scattering of an ionic fluid with liquid–liquid phase transition

Abstract

We report on the first static and dynamic light scattering measurements of near-critical behavior of an ionic fluid. The model system tetra-n-butylammonium picrate-tridecanol exhibits a liquid–liquid phase transition with an upper critical point near 342 K. The correlation lengths and scattering intensities scale with temperature corresponding to mean-field behavior. The data are also concordant with nonclassical 3D-Ising exponents if suitable Wegner corrections are applied. The spherical model recently suggested to apply for ionic fluids can be ruled out, thus resolving a current controversy in the literature.