A detailed semiempirical quantum chemical study of the lowest excited states of the shortest unsubstituted PDA oligomers C4n-2H2n, was carried out to determine the geometry, symmetry, excitation energy, ordering and oscillator strength of their lowest singlet and triplet states. The spectroscopic transition and the symmetry of the lowest singlet excited states were related to the fluorescence properties. Further, the efficiency of the decay of the lowest singlet excited state to generate two triplets through the so-called singlet fission process was detailed.
Musso, G. F., Comoretto, D., de Melas, F., Cuniberti, C., & Dellepiane, G. (1999). Excited states of polydiacetylene oligomers. Synthetic Metals, 102(1–3), 1414–1415. https://doi.org/10.1016/S0379-6779(98)00810-8