Resonance Transfer of Electronic Excitation Energy in Solution. II. The System p-Terphenyl−9-methylanthracene

Excitation resonance transfer between p-terphenyl (donor) and 9-methylanthracene (acceptor) was measured using methanol, ethanol, iso-propanol, tert-butanol, cyclohexanol, and cyclohexane as solvents. Förster's theory and the influence of Brownian motion on the process, as outlined in Part I, were tested. It was found that energy transfer occurred somewhat more readily than predicted. The acceptor concentration at which the fluorescence yield decreased to half its original value was c0.5=6.0×10−3M instead of the calculated 8.3×10−3M. This corresponds to a critical distance R°=31 Å instead of 27.8 Å. The influence of the diffusional movement of donor relative to acceptor as reflected by solvent viscosity was found to agree with the calculated value within the experimental error limits. A method for the separation of radiative and nonradiative energy transfer is described.