PHOTOPHYSICS OF POLYCYCLIC AROMATIC-HYDROCARBONS ADSORBED ON SILICA-GEL SURFACES .3. FLUORESCENCE QUANTUM YIELDS AND RADIATIVE DECAY-RATE CONSTANTS DERIVED FROM LIFETIME DISTRIBUTIONS

The fluorescence quantum yields of six polycyclic aromatic hydrocarbons (PAHs) adsorbed on both hydroxylated and highly dehydroxylated silica gel surfaces have been measured, using a diffuse reflectance method, an integrating sphere method, and a secondary method based on diffuse reflectance. Consistent results were obtained from these different procedures. Radiative and nonradiative decay rate constants of these systems were derived from these quantum yield data together with the lifetime distribution data obtained previously. These decay rate data, when compared with those obtained for the same PAHs in fluid media, appear reasonable.