Studies of photoexcited states in polyacetylene and poly(parpahenylenevinylene) by absorption detected magnetic resonance: the case of neutral photoexcitations

Photoexcited states in trans polyacetylene [f-(CH).x ] and in alkoxy derivatives of poly(paraphenylenevinylene) (PPV) have been studied by the technique of absorption detected magnetic resonance. In addition to the stable charged photoexcitations, which are charged solitons in f-(CH).x and bipolarons in PPV, we clearly identify neutral photoexcitations with nonzero spins. In / - (CH)x these are spin- j 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.