Electron-Electron Interactions and Resonant Optical Spectral Shifts in Photoreceptor Molecules

Abstract

The purpose of this paper is to discuss the optical excitation spectrum and electron-electron interactions in a Rhodopsin-like molecule. The task of the theory here is to provide some initial insight into the microscopic behaviour of these photoreceptor molecules and must, considering the complexity of the system involved, be semiempirical and somewhat speculative. Such a preliminary approach is usually required in understanding physical systems. A full microscopic theory of a phenomenon rarely comes out of the blue, but is almost always preceded by a period of interplay between approximate and semiempirical theory and experiment. It is in such a spirit that this paper is presented. This work has benefited from and is related to the work of W.A. Little (1, 2, 3) on the possible occurrence of a superconducting state in macromolecules. Little’s theory (1, 2, 3) suggested that certain special types of macromolecules and solids should exhibit superconductivity at room temperature. Unfortunately, as far as can be checked, no one has ever synthesised a structure which has seriously tested the predictions of the theory. Little’s proposal, then, is neither substantiated nor is it discredited.