Nonscaling displacement distributions as may be seen in fluorescence correlation spectroscopy

S. M. J. Khadem and I. M. Sokolov
Phys. Rev. E 95, 052139 – Published 24 May 2017

Abstract

A continuous time random walk (CTRW) model with waiting times following the Lévy-stable distribution with exponential cutoff in equilibrium is a simple theoretical model giving rise to normal, yet non-Gaussian, diffusion. The distribution of the particles' displacements is explicitly time dependent and does not scale. Since fluorescent correlation spectroscopy (FCS) is often used to investigate diffusion processes, we discuss the influence of this lack of scaling on the possible outcome of the FCS measurements and calculate the FCS autocorrelation curves for such equilibrated CTRWs. The results show that although the deviations from Gaussian behavior may be detected when analyzing the short- and long-time asymptotic behavior of the corresponding curves, their bodies are still perfectly fitted by the fit forms used for normal diffusion. The diffusion coefficients obtained from the fits may however differ considerably from the true tracer diffusion coefficients as describing the time dependence of the mean squared displacement.

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  • Received 21 March 2017

DOI:https://doi.org/10.1103/PhysRevE.95.052139

©2017 American Physical Society

Physics Subject Headings (PhySH)

Statistical Physics & Thermodynamics

Authors & Affiliations

S. M. J. Khadem and I. M. Sokolov

  • Institute of Physics, Humboldt University Berlin, Newtonstrasse 15, D-12489 Berlin, Germany and School of Analytical Sciences Adlershof (SALSA) Albert-Einstein-Strasse 5-9, D-12489 Berlin, Germany

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Issue

Vol. 95, Iss. 5 — May 2017

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