Origin of the stabilization energy of perylene excimer as studied by fluorescence and near-IR transient absorption spectroscopy

The origin of the stabilization energy of perylene excimer in toluene has b een studied. In order to measure the fluorescence spectra and its decay pro files under the condition free from the reabsorption effect, we designed a thin optical cell with a path length of about 10 mum. From the results, the photophysical parameters of perylene excimer such as the formation rate co nstant, the peak position and the lifetime and the quantum yield of fluores cence can be obtained. Using these values, the binding energy of perylene e xcimer can be evaluated as 0.44 eV from the temperature dependence of the t ransient absorption. By analyzing the band shape of the charge transfer abs orption in near-IR wavelength range, the transfer integral V between a neut ral excited state and an ion-pair state can be estimated as 0.37 eV. From t hese results, we conclude that the stabilization energy of perylene excimer consists of two components: exciton interaction (70%) and charge transfer interaction (30%). We also discuss the origin of the stabilization energy o f other aromatic excimers on the basis of the results on perylene excimer. (C) 2001 Elsevier Science B.V. All rights reserved.