High pressure studies of solvent effects on anthracene spectra

Measurements have been made of the effect of pressure on the peak location and peak shape for anthracene in a variety of liquid and plastic environments; both absorption and fluorescence studies were made. The results are discussed from two standpoints: in terms of the dielectric model and of a configuration coordinate model. For the latter model, the change of configuration coordinate (volume decrease of the system upon electronic excitation) is shown to correlate well with the product of the compressibility and polarizability of the solvent. For the dielectric model, it is found that the change of cavity volume with density is complex. However, the relative cavity volume obtained from emission measurements was consistently 10-15% smaller than that obtained from absorption. The cavity volume decreased with increasing polarizability of the solvent, and results obtained from absorption and emission were quite consistent in this regard.