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Appendices

FCS Classroom

Autocorrelation Due to Other Phenomena

Combining Fast Phenomena into a Correction Factor

Intersystem crossing time constants (discussed in Autocorrelation Due to Intersystem Crossing (Triplet State)) are typically in the range of microseconds. Unfortunately, there are a number of phenomena which share this domain. These include rotational diffusion rates and, if one is using photomultiplier tubes for detection, after-pulsing phenomena. As a result, and particularly when using photomultipliers, one has to view this region as part of a system correction.

To take into account all these phenomena we can rewrite the three-dimensional autocorrelation equation that includes intersystem crossing (see Autocorrelation Due to Intersystem Crossing (Triplet State)) as

equation
. (1)

Where A and τC are the correction coefficients and time constants respectively.

Additional Physical Models

See our List of FCS Equations for Various Physical Processes for autocorrelation models for additional processes.