title: Photon statistics and speckle visibility spectroscopy with partially coherent X-rays.
abstract: A new approach is proposed for measuring structural dynamics in materials from multi-speckle scattering patterns obtained with partially coherent X-rays. Coherent X-ray scattering is already widely used at high-brightness synchrotron lightsources to measure dynamics using X-ray photon correlation spectroscopy, but in many situations this experimental approach based on recording long series of images (i.e. movies) is either not adequate or not practical. Following the development of visible-light speckle visibility spectroscopy, the dynamic information is obtained instead by analyzing the photon statistics and calculating the speckle contrast in single scattering patterns. This quantity, also referred to as the speckle visibility, is determined by the properties of the partially coherent beam and other experimental parameters, as well as the internal motions in the sample (dynamics). As a case study, Brownian dynamics in a low-density colloidal suspension is measured and an excellent agreement is found between correlation functions measured by X-ray photon correlation spectroscopy and the decay in speckle visibility with integration time obtained from the analysis presented here.
authors.affiliation: Photon Sciences Directorate, Brookhaven National Laboratory, Upton, NY 11973, USA.
authors.forename: Luxi
authors.initials: L
authors.lastname: Li
authors.affiliation: European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble, France.
authors.forename: Paweł
authors.initials: P
authors.lastname: Kwaśniewski
authors.affiliation: Department of Physics and Earth Sciences, University of Parma, Parma, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Orsi
authors.affiliation: Photon Sciences Directorate, Brookhaven National Laboratory, Upton, NY 11973, USA.
authors.forename: Lutz
authors.initials: L
authors.lastname: Wiegart
authors.affiliation: Department of Physics and Earth Sciences, University of Parma, Parma, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Cristofolini
authors.affiliation: Stanford Linear Accelerator Laboratory, Menlo Park, CA 94025, USA.
authors.forename: Chiara
authors.initials: C
authors.lastname: Caronna
authors.affiliation: Photon Sciences Directorate, Brookhaven National Laboratory, Upton, NY 11973, USA.
authors.forename: Andrei
authors.initials: A
authors.lastname: Fluerasu
keywords: partially coherent X-rays; photon statistics; speckle visibility spectroscopy