In the double exponential decay of the emitted photoflux from an excited material the photoflux phi can be expressed by. K k is a real number such that. T time generally t 0 in control engineering.
Exponential decay is the change that occurs when an original amount is reduced by a consistent rate over a period of time.
Then we can re-write the function this way. The only difference is the value of the constant k. Higher values of k lead in a sense to faster decay. It is computed as the reciprocal of K.