Electronic spectral shifts, reorganization energies, and local density augmentation of Coumarin 153 in supercritical solvents

Abstract

Solvent reorganization energies and local densities of Coumarin 153 (C153) in supercritical C 2H 6, CO 2, and CHF 3 ( T c=5 K) are measured using fluorescence spectroscopy. Reorganization energies are 320±70 and 770±70 cm −1 in CO 2 and CHF 3, respectively – nearly independent of density (0.3≤ ρ/ ρ c≤2.1). The spectral shifts imply similar effective local densities in all three solvents. These effective densities can exceed 3–5 times the bulk density. In CO 2 and CHF 3, the maximum density augmentation calculated from emission shifts is ∼20% greater than that calculated from excitation shifts. No such difference is found in C 2H 6.