Recurrence and photon statistics in fluorescence fluctuation spectroscopy

The recurrence of fluorescence fluctuations of nanoparticles diffusing through a laser focus were investigated. Probability distribution functions (PDF) of on and off periods were determined upon a threshold number θ of photons. The patterns of the on and off periods revealed a self-similar structure indicating a pronounced scaling behavior of the on and off periods. The results confirm that this diffusion-reaction equation provides an accurate description of the PDFs taking into account diffusion and photon statistics on equal footing and including the multiple particle problem for off states.