Interaction of triplet excitons with excited naphthalene and deuteronaphthalene molecules in benzophenone crystals

Abstract

An increase in the intensity of the exciting light is shown to cause a significant decrease in the quantum yield and rise time of the sensitized phosphorescence of impurity C₁₀H₈ and C₁₀D₈ in benzophenone crystals. Nonlinear quenching of the impurity phosphorescence occurs because one or two excitations are quenched in the interaction of triplet excitons with impurity molecules in the excited state in which they are left after the first exciton capture. Experiments show the nature of the changes in the quantum yield and the rise time of the impurity phosphorescence as the exciting-light intensity is varied from 3.6 · 10¹² to 6 · 10¹⁶ photons/cm² · sec depends strongly on the impurity concentration, the crystal thickness, and the lifetime of the triplet state of the impurity molecules. The experimental results are in good agreement with a proposed theory for the kinetics of the interaction of triplet excitons with impurity molecules in the ground and triplet states.