title: Observation of surface layering in a nonmetallic liquid.
abstract: Oscillatory density profiles (layers) have previously been observed at the free surfaces of liquid metals but not in other isotropic liquids. We have used x-ray reflectivity to study a molecular liquid, tetrakis(2-ethylhexoxy)silane. When cooled to T/Tc approximately 0.25 (well above the freezing point for this liquid), density oscillations appear at the surface. Lateral order within the layers is liquidlike. Our results confirm theoretical predictions that a surface-layered state will appear even in dielectric liquids at sufficiently low temperatures, if not preempted by freezing.
authors.affiliation: Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA.
authors.forename: Haiding
authors.initials: H
authors.lastname: Mo
authors.forename: Guennadi
authors.initials: G
authors.lastname: Evmenenko
authors.forename: Sumit
authors.initials: S
authors.lastname: Kewalramani
authors.forename: Kyungil
authors.initials: K
authors.lastname: Kim
authors.forename: Steven N
authors.initials: SN
authors.lastname: Ehrlich
authors.forename: Pulak
authors.initials: P
authors.lastname: Dutta