GAUSSIAN APPROXIMATION TO THE UNIQUE HETEROGENEOUS LANGMUIR-HINSHELWOOD TYPE FLUORESCENCE QUENCHING AT THE SILICA-GEL GAS-SOLID INTERFACE - PYRENE AND 9,10-DIPHENYLANTHRACENE SINGLET QUENCHING BY OXYGEN

The temperature dependency of the oxygen quenching of the singlet excited states of both pyrene and 9,10-diphenylanthracene on nonporous silica gel has been studied by both laser-induced time-resolved and steady-state fluorescence spectroscopy. A Gaussian distribution of rate constants is presented to account for the heterogeneous kinetics. Oxygen adsorption isotherms on the silica gel surface above the gas/liquid critical temperature are determined; oxygen assimilation times of 23.2, 44.1, 99.5, and 238 ps have been calculated at -47, -64, -80, and -98°C, respectively. A dynamic Langmuir-Hinshelwood model for the bimolecular quenching reaction is presented. © 1990 American Chemical Society.