Total and Radiative Triplet-Triplet Exciton-Annihilation Rate Constant in Pyrene Crystals

Abstract

The total and the radiative rate constants for triplet-triplet exciton annihilation have been determined in pyrene single crystals. The values are ${\gamma }_{\mathrm{tot}}=(7.5\mathrm{}\pm 4.0)\times {10}^{-12\mathrm{}}$ ${\mathrm{cm}}^3$ ${\sec }^{-1\mathrm{}}$ and ${\gamma }_{\mathrm{rad}}=(2.0\mathrm{}\pm 1)\times {10}^{-12\mathrm{}}$ ${\mathrm{cm}}^3$ ${\sec }^{-1\mathrm{}}$, respectively. The fraction of triplet fusions leading to singlets is 0.19 × 0.02. A simple procedure is presented which allows the determination of the product $\alpha {\gamma }_{\mathrm{tot}}$ where $\alpha$ is the ground-state-singlet-first-excited-triplet absorption coefficient of the material.