Boundary conditions and optical absorption in the soliton model of polyacetylene

In the present paper the boundary conditions and the optical absorption are studied for both the discrete and continuum models of solitions in polyacetylene. The topological property of the soliton is incorporated appropriately to derive the correct boundary conditions for the electronic wave functions which are essential for a proper calculation of optical absorption and other properties of the system. A general sum rule for the absorption coefficient is derived for the continuum model which is exactly satisfied by the result of the present calculation. The errors in the previous calculations are indicated. Finally, the theoretical results are compared with the experimental data.