The Recovery Of Underlying Lifetime Distributions From Fluorescence Decay Data
In this thesis, two methods for recovering underlying lifetime distributions from single photon counting fluorescence decay data are described, namely the Exponential Series Method (ESM) and the Maximum Entropy Method (MEM). Extensive testing of these two methods is performed, using both real and simulated decay curves, in order to establish their abilities and limitations, especially with respect to the resolution of discrete lifetimes, the accurate recovery of broad distribution shapes, and the ability to distinguish conclusively between these two cases. The effect of data precision, relative separation in {dollar}tau{dollar}-space of the discrete lifetimes or distributions, and experimental noise on the performance of these methods is fully investigated. Both methods are found to be able to resolve sets of discrete lifetimes, with resolution improving as relative separation of the lifetimes and precision of the decay is increased. MEM is found to have slightly better resolving power than ESM. Background noise is found to interfere with this resolution, and must be properly treated. Distribution shapes are found to be well recovered by both methods, with MEM having a slightly greater tendency to distort the shape than ESM.;The two methods are applied to three experimental systems: Forster transfer in rigid media, Forster transfer in viscous media, and intramolecular quenching in homotryptophan esters. Broad, reproducible distributions are recovered in all three cases. These applications are used to illustrate the usefulness of distribution analyses for dealing with complex photophysical systems.
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