Singlet Energy Transfer in p-Terphenyl Crystal Doped with Tetracene

The transfer of singlet energy in p-terphenyl crystal was measured as a function of the dopant (tetracene) concentration and the temperature. The simple hopping model yields a value of 3×10−14 s. This value is believed to be correct within a factor of 5. In the low temperature phase of the crystal, the energy transfer is temperature dependent with an activation energy of 66 cm−1 in undeuterated p-terphenyl and 90 cm−1 in perdeuterated p-terphenyl. It seems probable that in the low temperature phase the freedom of the conformational change of the molecule plays an important role in the energy migration.