title: X-ray studies of the interface between two polar liquids: neat and with electrolytes.
abstract: We demonstrate the use of X-ray reflectivity to probe the electron density profile normal to the interface between two polar liquids. Measurements of the interfacial width at the neat nitrobenzene/water and the neat water/2-heptanone interfaces are presented. These widths are consistent with predictions from capillary wave theory that describe thermal interfacial fluctuations determined by the tension and bending rigidity of the interface. Variation of the temperature of the water/nitrobenzene interface from 25 degrees C to 55 degrees C indicates that the role of the bending rigidity decreases with increasing temperature. X-ray reflectivity measurements of the electrified interface between an aqueous solution of BaCl2 and a nitrobenzene solution of TBATPB demonstrate the sensitivity of these measurements to the electrolyte distribution at the interface. A preliminary analysis of these data illustrates the inadequacy of the simplest, classical Gouy-Chapman theory of the electrolyte distribution.
authors.affiliation: Department of Physics (M/C 273), University of Illinois at Chicago, Chicago, IL 60607-7059, USA.
authors.forename: Guangming
authors.initials: G
authors.lastname: Luo
authors.forename: Sarka
authors.initials: S
authors.lastname: Malkova
authors.forename: Sai Venkatesh
authors.initials: SV
authors.lastname: Pingali
authors.forename: David G
authors.initials: DG
authors.lastname: Schultz
authors.forename: Binhua
authors.initials: B
authors.lastname: Lin
authors.forename: Mati
authors.initials: M
authors.lastname: Meron
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Graber
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Gebhardt
authors.forename: Petr
authors.initials: P
authors.lastname: Vanysek
authors.forename: Mark L
authors.initials: ML
authors.lastname: Schlossman