SPECIFYING BOUNDS ON THE RATE CONSTANTS OF INTRAMOLECULAR 2-STATE EXCITED-STATE PROCESSES BY GLOBAL COMPARTMENTAL ANALYSIS OF THE FLUORESCENCE DECAY SURFACE

This report is an extension of the identifiability study [Boens et al. . J. Phys. Chem. 96 (1992) 6331-6342] of intramolecular two-state exci ted-state processes. The identifiability study is expressed in terms o f the rate constants and the parameters b1 and c1, where b1 is the rel ative absorbance of ground-state species 1 and c1 is the normalized sp ectral emission weighting factor of the corresponding excited-state sp ecies 1. From the decay times and the preexponential factors of a sin gle fluorescence decay trace. it is generally possible to derive two s ets of rate constants when one rate constant, b1 and c1 are known befo rehand. A unique set of rate constants can be obtained when one rate c onstant is known in combination with the following sets of values for (b1, c1): (0.5, 1), (0.5, 0), (1, 0.5). (0, 0.5), (0.5, 0.5), (1, 1) o r (0, 0). It is further shown that when (b1, c1) equals (1, 1) or (0, 0), i.e. a single species is excited and the fluorescence of only that species is observed, upper and lower bounds on all rate constants can be specified without any a priori information about the rate constant values. The bounds on the rate constants can be specified in terms of the decay times and the preexponential factors estimated from the bie xponential analysis of a single fluorescence decay trace with b1 = 1 a nd c1 = 1 or, equivalently, b1 = 0 and c1 = 0. This analysis approach can provide kinetic information of intramolecular electron transfer an d exciplex formation when no suitable model compound is available.