where k d is the deprotonation rate constant. A finite interval τ may be subdivided into n = τ δτ small time intervals δτ . Assuming statistical independence of events in successive time intervals (Markov process) 99,100 , the probability p H (τ ) for a molecule to remain protonated during the entire interval τ may be calculated as the product of the individual probabilities. In the limit of large n the probability p H (τ ) becomes