Theory of polarization quenching by excitation transfer

Abstract

The theory of concentration quenching of fluorescence polarization for three-dimensional solutions in which the dipolar positions and orientations are randomly distributed is investigated by examining and extending the theories of Förster, of Ore, and of Knox (Paper I) through the use of numerical methods. Rigorous results are obtained which allow each initially excited molecule to share its excitation with both its nearest and next nearest neighbours (in contrast to the original theories of Förster and Ore in which only the nearest neighbour is explicitly considered) using the isotropic form of the Förster transfer mechanism. The results of Jablonski's theory, our original theory, our extension of the calculations, and our extension of Ore's theory, now predict values of the Förster parameter R ₀ which differ from each other by less than 4 per cent. The results are compared with three different sets of experimental data.