K. Teuchner et al., Instantaneous fluorescence quantum yield - A new quantity with characteristic "fingerprints" for excited-state processes, J FLUORESC, 9(1), 1999, pp. 67-71
The instantaneous fluorescence quantum yield phi(ins)-a new quantity for fl
uorescence studies defined as the ratio of the fluorescence intensity to th
e optical density, both measured at the moment of the maximum of the exciti
ng pulse-proves to be a very sensitive function for excited-state processes
. Dependent on the excitation intensity phi(ins) exhibits characteristic fe
atures (maxima/minima) indicating, for example, excited-state absorptions a
nd annihilation processes. phi(ins) is therefore more informative as the in
tensity dependence of the usually utilized fluorescence yield, the informat
ion content of which is restricted because this function is hardly structur
ed. In the paper the influences of specific molecular parameters (excited-s
tate absorption cross section, annihilation constant) on phi(ins) are given
, problems of the experimental accessibility of phi(ins) are discussed, and
an experimental setup for determination of this new quantity is presented.
The application of the method is demonstrated for identification of excite
d-state absorptions of organic molecules in solution.