Abstract
The color generation mechanism has been reviewed from the standpoint of excitonic interactions. In dyes and pigments, delocalization of the excited state (so-called exciton state) takes place upon light excitation because the absorption coefficient of the component molecule is quite high. The excitonic interaction (i.e. interaction between transition dipoles)induces a spectral shift or splitting (Davydov splitting) in the solid state, giving rise to a quite different absorption spectrum from the molecular one. The present process has been theoretically reviewed together with some examples of organic pigments.
