ABSTRACT
Simplicity and accuracy are effectively combined in introductory textbooks, where transparent derivations based on idealized models are routinely augmented by numerical results and experimental comparisons reflecting the most comprehensive development along the same lines. This strategy is pursued for low-lying excited states, with special attention to novel features associated with electron-phonon and electron-electron interactions. This chapter discusses applications, often preliminary or incomplete, involving more realistic models of polymers. Chemical differences between conjugated polymers minimally require a quantum-chemical description of the unit cell even within an idealized, single-strand picture. The parametrization of quantum cell models is related to molecular systems that afford richer and more precise data. The consequences of finite chain lengths, of different polymer conformations, and of interchain interactions are sketched, with special emphasis on necessary modifications to infinite idealized strands. The chapter summarizes a phenomenological approach to vibronic coupling due to backbone vibrations and related to the question of e-e contributions.
