Triplet-exciton generation mechanism in a new soluble (red-phase) polydiacetylene

The time scale of covalent state relaxation and singlet fission into triplet pairs is determined in a solution of-isolated polydiacetylene chains showing a remarkably sharp excitonic transition by applying the transient transmission difference spectroscopy technique with sub-10 fs optical pulses. Photoexcitation into, the band of ionic states is followed by a branching within the first 100 fs which populates the band of covalent states. The latter start. to dissociate into triplet excitations, completing the process in about 300 fs.