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Introduction
Figure 1.13: Simulated time domain traces for a fluorophore that exhibits a 1, 5, and 10
ns excited-state lifetime.
be fitted to a sum of exponentials:
I(t) =
n
αie −t/τi (1.14)
i=0
where αi is the pre-exponential factor denoting the contribution to the total time-
resolved decay of the component with lifetime τi. Figure 1.14 shows situation where
there are two fluorophores with different lifetimes, one short and one long lifetime
component. The fraction of the steady state intensity due to each component is
given by:
fi = αiτi
j
αjτj
(1.15)
For TD experiments, the intensity of the decay (I(t)) is convolved with the Instru-
ment Response Function (IRF). The IRF represents the response of the measure-
ment system to the excitation pulse and can be generated by recording the output
from a sample that scatters the excitation light or a fluorophore of very short life-
time. The convolution of the (IRF(t)) and the sample decay results in an observed
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