Fluorescence quenching in laser dyes by absorption from an excited singlet state

The effects of absorption of pump radiation from the first excited singlet state on the fluorescence quantum yield are calculated by numerical solution of simple rate equations, and compared with experiments performed earlier for the dye 7-diethylamino-4-methyl-coumarin at N₂-laser pumping. Analytical solutions for high and low pump intensities are found for the case of an optically thin solution.