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The autocorrelation function (ACF) relates the fluctuation in
scattered intensity to the diffusion coefficient. The specific
algorithm for calculating an ACF varies based on the so ware
provided. It is also influenced by the optics setup within your
instrument. Despite these differences, ACF plots have many key
properties in common. It is important to understand what the ACF
plot is showing you in order to be able to evaluate data quality.
The autocorrelation function
A note about nomenclature: while we describe the
scattering of a single particle for the sake of clarity,
what we're really examining is the overall fluctuation
in a system. The ACF fit is applied to all particles that
scatter within the range of the detector, which is why
we can use it to determine the distribution of particle
sizes within a sample.
