On the Optical Properties of all-<i>trans</i> Carotenoids

Abstract

Previous LCAO-ASMO-SCF-CI calculation on the π-electron system in carotenoids has been defective in the following two respects. Firstly, the relation between bond order and bond distance assumed tentatively there (being a phenomenological description of the σ-π interaction by which the bond alternation is caused) seems to be not necessarily reasonable. Secondly, a sufficient number of singly- and doubly-excited singlet-configurations have not been included in the CI calculation, so that there have remained some ambiguities in the parametrization. The purpose of the present paper is to remedy these faults of the previous calculation, to establish a firm foundation for the explanation of the optical properties of carotenoids in photoreceptor systems.