Excited polarons in poly(phenylene vinylene) and poly(diacetylene).

We have employed the Su-Schrieffer-Heeger Hamiltonian to calculate the depths ${\mathrm{\ensuremath{\omega}}}_{0}$/${\mathrm{\ensuremath{\Delta}}}_{0}$ of the intragap states and binding energies ${\mathrm{\ensuremath{\varepsilon}}}_{\mathit{B}}$ of a variety of nonlinear excitations in poly(phenylene vinylene) and poly(diacetylene). These include the electronically excited polaron and polarexciton in which an electron has been promoted from a lower to an upper intragap level. The results for ${\mathrm{\ensuremath{\varepsilon}}}_{\mathit{B}}$ indicate a series of defect-pair annihilation processes that may be relevant to nonradiative decay of the polarexciton. The results for ${\mathrm{\ensuremath{\omega}}}_{0}$/${\mathrm{\ensuremath{\Delta}}}_{0}$ show that the dependence of ${\mathrm{\ensuremath{\omega}}}_{0}$/${\mathrm{\ensuremath{\Delta}}}_{0}$ on the soliton-confinement parameter \ensuremath{\gamma} for the bipolaron is quantitatively different from that given by the Brazovskii-Kirova relation.