Analytical model of the fluorescence fluctuation spectroscopy experiment

The mathematical formalism of generating functionals was adopted for the un ified statistical description of a typical experiment in fluorescence fluct uation spectroscopy. The generating functionals formalism leads to a set of functional equations, Linking the statistical characteristics of the excit ation and detected photons via the characteristics of a molecular system. T he statistical characteristics of the detected photons can then be obtained in a straightforward and consistent way. We particularly show how characte ristics such as the photocount correlation function and the probability dis tribution of the number of photocounts per detection interval can be derive d based on the developed theory. We further demonstrate that the probabilit y density distribution of the first and single photocount time occurrences in the detection interval also Can be used for probing molecular behavior. The presented approach is applicable to a broad range of experimental confi gurations (continuous and pulsed excitation, one-photon and two-photon lase r excitation, scanning laser excitation) and molecular movements (diffusion in two and three dimensions, fluid flows). (C) 2001 American Institute of Physics.