Triplet exciton diffusion and double photon absorption in tetracene

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Delayed fluorescence from tetracene crystal excited at 8600 Å is studied. The luminescence decay is interpreted in terms of a model in which singlets are generated by triplet exciton fusion and by double‐photon absorption. The double‐photon absorption coefficient is estimated to be 5.8 × 10 ―27 cm s. The triplet exciton diffusion coefficient along the crystal b axis is determined by the spatial intermittency method to be (4 ± 1) × 10 ―3 cm 2 /s. The influence of this diffusion coefficient on other processes is discussed.