Studies of photoexcited states in polyacetylene and poly(paraphenylenevinylene) by absorption detected magnetic resonance: The case of neutral photoexcitations.

Photoexcited states in trans polyacetylene lt-(CH), l and in ulkoxy derivatives of poly(puraphenylenevinylene) (PPV) have been studied by the technique of absorption detected magnetic resonance. In addition to the stable charged photoexcitations, which are charged solitons in t-(CH), and bipolarons in PPV, we clearly identify neutral photoexcitations with nonzero spins. In t-(CH), these are spin—, ' neutral solitons S" (S") with an optical transition at 1.35 eV. The neutral photoexcitations in PPV form triplet excitons which cannot dissociate into S"S"pairs due to the confinement caused by the nondegenerate backbone structure.