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The signal is analysed by calculating the intensity [[autocorrelation]] function called g<sub>2</sub>.
<math>g_2(\tau)=\frac{
For the case of non-interacting particles suspended in a (complex) fluid a direct relation between g<sub>2</sub>-1 and the mean square displacement of the particles <Δr<sup>2</sup>> can be established. Let's note P(s) the probability density function (PDF) of the photon path length s. The relation can be written as follows:<ref>
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}}</ref>
<math>g_2(\tau)-1=[\int {ds P(s) \exp(-(s/l*)k_0^2
with <math>k_0=\frac{2\pi n}{\lambda}</math> and <math>l*</math> is the transport mean free path of scattered light.
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For simple cell geometries, it is thus possible to calculate the mean square displacement of the particles <Δr<sup>2</sup>> from the measured g<sub>2</sub>-1 values analytically. For example, for the backscattering geometry, an infinitely thick cell, large laser spot illumination and detection of photons coming from the center of the spot, the relation ship between g<sub>2</sub>-1 and <Δr<sup>2</sup> is:
<math>g_2(\tau)-1=\exp
For less thick cells and in transmission, the relationship depends also on l* (the transport length).<ref>
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