Triplet—Triplet Annihilation in Anthracene at Low-Excitation Intensities: Wavelength and Temperature Dependence

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Abstract
The process of triplet—triplet annihilation in crystalline anthracene has been investigated at low‐excitation intensities using a cw xenon‐arc‐lamp source. Bimolecular annihilation is observed by means of a subsequent fluorescence decay from the first excited singlet state to the ground state. The dependence of this fluorescence signal upon excitation power and excitation wavelength has been measured, as well as the temperature dependence, in the range from 80° to 500°K, of the cw fluorescence power and the fluorescence decay constant. The variations of fluorescence power and fluorescence decay constant with temperature can be explained by assuming the presence of two distinct trap levels for the triplet excitons.
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