STUDIES OF PHOTOEXCITED STATES IN POLYACETYLENE AND POLY(PARAPHENYLENEVINYLENE) BY ABSORPTION DETECTED MAGNETIC-RESONANCE - THE CASE OF NEUTRAL PHOTOEXCITATIONS

Photoexcited states in trans polyacetylene [t-(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 t-(CH)x and bipolarons in PPV, we clearly identify neutral photoexcitations with nonzero spins. In t-(CH)x these are spin-1/2 neutral solitons S0 (SBAR0) with an optical transition at 1.35 eV. The neutral photoexcitations in PPV form triplet excitons which cannot dissociate into S0SBAR0 pairs due to the confinement caused by the nondegenerate backbone structure.