The determination of the site-energy distribution of organic molecules dissolved in glassy matrices

Abstract

We present a method that allows the determination of the distribution of 0–0 energies of organic molecules in glassy matrices. Starting with the assumption that the spectra of differently sited molecules in the glass have different origins but are otherwise identical, we develop an algorithm that allows the decomposition of the observed spectra into the contributions from the different sites and thus eliminate the strong inhomogeneous broadening which occurs in glassy matrices. The input data for our algorithm are site selection spectra excited at different energies. These spectra have been measured for the phosphorescence of 1-iodonaphthalene in bromobutane. The resulting site distribution has a Gaussian shape with a width of 190 cm−1. The simple theory developed is found to predict the observed shape and intensity measured for the phonon wing of the 0–0 transition for different excitation energies.