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The singlet–triplet (T1 ← S0) excitation spectrum for delayed fluorescence and the prompt fluorescence (S1 → S0) emission spectrum have been measured for a tetracene crystal at room temperature. The origin (0–0 transition) in the two spectra at 10 100 ± 20 and 18 680 ± 30 cm−1, respectively, imply the activation energy for singlet exciton fission, ΔE = 1520 ± 70 cm−1. Raman lines corresponding to the vibrational structure in the above spectra were detected. The fluorescence emission spectra show the need for taking reabsorption effects into account.
Tomkiewicz et al. (Sat,) studied this question.