ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
An ensemble of distributed donor molecules that undergoes rotational transitions into a discrete excimer state has been analyzed, in an attempt to model distributed electronic relaxation and nonexponential fluorescence of aromatic polymers in presence of rotational sampling processes. In case of irreversible trapping, the donor survival function has been formulated in terms of the one-sided Laplace transform and specified for a modified Gaussian distribution to yield a closed-form expression for the donor decay. The formalism permits a time-dependent rate function to be derived that makes possible the construction of the excimer excitation function by means of the convolution theorem. In case of reversible constraints, a generalized treatment based upon time-dependent transition and transform matrices has been given which applies a perturbation technique for approximately solving the system of nonautonomous differential equations in the time domain. In the limit of weak coupling, the method develops approximate Mth order expressions (M=2,4,6, and 8) to the fluorescence response functions of donor and excimer. The perturbational solutions are well behaved up to relatively long time scales and they prove useful for providing the typical nonexponential time behavior of such a system affected by dispersion and dissociation. The physical restriction of this mathematical analysis (weak reversibility) has been addressed and the implications of distributed event times in future analyses of polymer fluorescence have been discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.456857
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