Statistics of dwell times in a reaction with randomly fluctuating rates

Recent single-molecule fluorescence spectroscopy have been analyzed in terms of a reaction with a single fluctuating rate (Shenter, J. Phys. Chem A 103 (1999) 10 477). The fluctuations in that analysis are related to the solution of an O–U equation. We propose the use of a simpler type of fluctuation defined in terms of a random telegraph signal. We show that this is equivalent to a four-state Markov model, most of whose properties can be derived exactly in closed form.