Evidence for incoherent energy transfer processes in J-aggregates with Davydov splitting

The energy relaxation of J-aggregates exhibiting Davydov splitting is examined by temperature-dependent fluorescence lifetime measurements and time-resolved emission spectra. Experimental results like non-exponential decay behavior, a strong dependence of the fluorescence lifetimes on detection wavelength, and a time-dependent Stokes shift observed using short excitation wavelengths, can be explained when an incoherent energy hopping relaxation is assumed. The results are not consistent with the mechanism of a coherent energy migration.