Patent ID: 6965113

Claim:
A method for characterizing samples having fluorescent particles, comprising the steps of: a) monitoring intensity fluctuations of fluorescence emitted by the particles in at least one measurement volume by detecting sequences of photon counts by at least one photon detector, b) determining from the sequences of photon counts intermediate statistical data comprising at least two probability functions, {circumflex over (P)} 1 (n 1 ), {circumflex over (P)} 2 (n 2 ), . . . , of the number of photon counts, n 1 , n 2 , . . . , detected in different sets of counting time intervals, c) determining from said intermediate statistical data a distribution of particles as a function of at least two arguments, wherein one argument is a specific brightness of the particles, or a measure thereof, and another argument is a diffusion coefficient of the particles, or a measure thereof, wherein said distribution function of particles is determined by fitting the experimentally determined probability functions {circumflex over (P)} 1 (n 1 ), {circumflex over (P)} 2 (n 2 ), . . . by corresponding theoretical probability functions P 1 (n 1 ), P 2 (n 2 ), . . . and wherein said theoretical probability distributions P 1 (n 1 ), P 2 (n 2 ), . . . are calculated as functions of apparent concentrations and apparent brightness which depend on the widths of the counting time intervals in the different sets.