Correction of the afterpulsing effect in fluorescence correlation spectroscopy using time symmetry analysis.

Afterpulsing of a photon-counting detector is a common problem in fluorescence correlation spectroscopy. We have developed a numerical procedure which eliminates the afterpulsing effect by analyzing the time reversal asymmetry of photon data that are recorded with a time-correlated single photon counting device. This method was applied to experimental data and was compared with a previous method [Rev. Sci. Instrum. 76, 033102 (2005).]. It is demonstrated that the present method can completely eliminate the afterpulsing effect even in the case of a sample solution that contains multiple fluorophores having different fluorescence lifetimes, for which the previous method underestimates the correlation amplitude. We also show a modification of the previous method incorporating the time symmetry analysis.