Fluorescence correlation spectroscopy (FCS) is a laser spectroscopy technique that monitors correlations between molecules or particle motions in solutions or gels. It has numerous applications in physical chemistry, microscopy, biophysical chemistry, biochemistry and biomedicine, inclusiv detection of virus particles such as those causing HIV, and the papilloma viruses. It casn also be employed to determine diffusion coefficients and molecular diffusion curves/molecular paths and correlation times in the millisecond to picosecond range.

more to come... http : ∕∕planetphysics.org∕?op = getobj&from = papers&id = 126

See also -Fluorescence cross-correlation spectroscopy -Dynamic Light scattering - Fluorescence spectroscopy -Diffusion coefficient