see also:

FCS, fluorescence lifetime correlation spectroscopy (FLCS)

Fluorescence-correlation-spectroscopy is a highly sensitive, time-resolved optical measurement method that can be used to study the mobility of fluorescent particles and molecular interactions. The widely used measurement method is based on a confocal microscope and reveals interesting biochemical parameters. During measurement fluctuations in the fluorescence emission intensity over time are recorded, which are caused by individual fluorophores that pass through the detection volume. With FCS, the size or shape of particles, diffusion constants, concentrations, and bonds between different diffusing species can be determined. 

A combination of the time-correlated single photon counting (TCSPC) with the above-mentioned classic fluorescence correlation spectroscopy is called fluorescence lifetime correlation spectroscopy (FLCS). With this method, the time-resolved detection of fluorescence is used to separate the contribution of different processes to the measurement signal. The time resolution is in the picosecond range, which means that high-performance TDCs or ADCs are the best choices for data acquisition for such applications.

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