Photoproduction of neutral soliton pairs intrans-(CH)x

Despite the many successes of the soliton theory of (CH${)}_x$, the identity of the defect species responsible for the high-energy peak (∼1.4 eV) in the photoinduced absorption spectrum has remained unexplained, and has provided reason to doubt the validity of the simple independent-electron model on which the theory was based. Here we show that (1) the presence of even weak interactions which break the charge-conjugation symmetry of the continuum model permit the photogeneration of neutral soliton pairs in polyacetylene, (2) these pairs attract to form a bound state which, in the presence of disorder, can be highly metastable, and (3) these pairs provide a natural explanation for the high-energy peak and several other heretofore unexplained experimental observations.