LATTICE-RELAXATION OF EVEN-PARITY SINGLET EXCITED-STATES IN POLYACETYLENE AND 4-SOLITON BOUND-STATE

We have carried out a theoretical study of the lattice relaxation of some low-lying even-parity singlet excited states in polyacetylene. Both degenerate perturbation and strong coupling calculations give very similar results which indicate the relaxed configuration of the lowest singlet Ag excited state is a novel four-soliton bound state, with a binding energy of about 0.05 eV against dissociation into four free neutral solitons. Experimental implications of the theoretical findings are discussed. © 1995 The American Physical Society.