The theory of Part I of this series (McRae
1961) is developed in detail for dimeric systems. The simplest possible theory
of the exciton states for a system of two non-rigid molecules is obtained
through the use of perturbation theory. The theory makes possible the
prediction of electronic band structures in absorption and fluorescence spectra
as functions of the theoretical Davydov splitting for two rigid molecules.
Numerical calculations are made for a
dimer of a typical dye, and the results are compared with the observed
absorption spectrum of the 1,1'-diethyl-2,2'-pyridocyanine iodide dimer.