The role of solitons in the first B u excited state of polyene chains: From short polyenes to polyacetylene

Abstract

We present calculations on the geometry of the first 1B u excited state in polyene chains ranging in length from 5 to 29 double bonds. Calculations are performed in the framework of a Hückel Hamiltonian with bond-length-dependent transfer integrals and with σ-bond compressibility and use the parameters originally chosen for polyacetylene. Our results indicate that there is a smooth evolution of the 1B u excited state geometry relaxation on going from short to long chains. In all cases, we find that the 1B u excited state geometry tends to relax in such a way as to produce a pair of soliton defects. The implications of our results for the nonlinear optical properties of polyenes are discussed.