X-ray photon correlation spectroscopy (XPCS) in

physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which r ...

and

chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions ...

, is a novel technique that exploits a

coherent Coherence, coherency, or coherent may refer to the following: Physics * Coherence (physics), an ideal property of waves that enables stationary (i.e. temporally and spatially constant) interference * Coherence (units of measurement), a deri ...

X-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...

synchrotron A synchrotron is a particular type of cyclic particle accelerator, descended from the cyclotron, in which the accelerating particle beam travels around a fixed closed-loop path. The magnetic field which bends the particle beam into its closed p ...

beam to measure the dynamics of a sample. By recording how

coherent speckle Coherence, coherency, or coherent may refer to the following: Physics * Coherence (physics), an ideal property of waves that enables stationary (i.e. temporally and spatially constant) interference * Coherence (units of measurement), a deriv ...

fluctuations in time, one can measure a time correlation function, and thus measure the timescale processes of interest (diffusion, relaxation, reorganization, etc.). XPCS is used to study the slow dynamics of various equilibrium and non-equilibrium processes occurring in condensed matter systems.

Advantages

XPCS experiments have the advantage of providing us with the information of dynamical properties of materials (e.g. vitreous materials), while other experimental techniques can only provide information about the static structure of the material. This technique is based on the generation of a speckle pattern by the scattered coherent light originating from a material where some spatial inhomogeneities are present. A speckle pattern is a

diffraction Diffraction is defined as the interference or bending of waves around the corners of an obstacle or through an aperture into the region of geometrical shadow of the obstacle/aperture. The diffracting object or aperture effectively becomes a s ...

limited structure factor, and is typically observed when laser light is reflected from a rough surface, or from dust particles performing Brownian motion in air. The observation of speckle patterns with

hard X-rays X-rays (or rarely, ''X-radiation'') are a form of high-energy electromagnetic radiation. In many languages, it is referred to as Röntgen radiation, after the German scientist Wilhelm Conrad Röntgen, who discovered it in 1895 and named it ''X ...

has just been demonstrated in the last few years. This observation is only possible now because of the development of new

synchrotron radiation Synchrotron radiation (also known as magnetobremsstrahlung radiation) is the electromagnetic radiation emitted when relativistic charged particles are subject to an acceleration perpendicular to their velocity (). It is produced artificially in ...

X-ray sources that can provide sufficient coherent

flux Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications to physics. For transport ph ...

aXPCS

A specific subgroup of these techniques is atomic-scale X-ray photon correlation spectroscopy (aXPCS).

References

{{Reflist

Sources

* P.-A. Lemieux, D.J. Duria
Investigating non-Gaussian scattering processes by using nth-order intensity correlation functions
''Journal of the Optical Society of America'' 1999, 16(7), 1651–1664
doi: 10.1364/JOSAA.16.001651
* Robert L. Lehen
XPCS: Nanoscale motion and rheology
''Current Opinion in Colloid & Interface Science'' 2012, 17 (1), 3–12
doi: 10.1016/j.cocis.2011.11.002
*Oleg G. Shpyrk

''J. Synchrotron Radiation'' 2014, 21 (5), 1057–1064
doi: 10.1107/S1600577514018232
* Sunil K. Sinha, Zhang Jiang, Laurence B. Luri
X-ray Photon Correlation Spectroscopy Studies of Surfaces and Thin Films
''Advanced Materials'' 2014, 26 (46), 7764–7785
doi: 10.1002/adma.201401094
* Aurora Nogales, Andrei Flueras
X Ray Photon Correlation Spectroscopy for the study of polymer dynamics
''European Polymer Journal'' 2016
doi: 10.1016/j.eurpolymj.2016.03.032
Synchrotron-related techniques X-ray spectroscopy