title: On the use of two-time correlation functions for X-ray photon correlation spectroscopy data analysis.
abstract: Multi-time correlation functions are especially well suited to study non-equilibrium processes. In particular, two-time correlation functions are widely used in X-ray photon correlation experiments on systems out of equilibrium. One-time correlations are often extracted from two-time correlation functions at different sample ages. However, this way of analysing two-time correlation functions is not unique. Here, two methods to analyse two-time correlation functions are scrutinized, and three illustrative examples are used to discuss the implications for the evaluation of the correlation times and functional shape of the correlations.
authors.affiliation: Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK; XMaS, The UK-CRG Beamline, ESRF - The European Synchrotron, CS40220, F-38043 Grenoble Cedex 09, France.
authors.forename: Oier
authors.initials: O
authors.lastname: Bikondoa
keywords:  two-time correlation functions; X-ray photon correlation spectroscopy; data analysis