Derivation and interpretation of the spectra of aggregates. Part 4.—Adiabatic theory of exciton interactions in dimers

Abstract

The adiabatic approximation has been applied to the problem of exciton interactions in dimers. It is determined that a weak interaction, arising from the nuclear kinetic energy, exists between the ground state and excited state within each molecule in the dimer and that, indirectly, this interaction introduces an additional significant coupling between the excited states of the dimer. The problem which includes such “kinetically induced” effects is formulated and solved for the usual tightbinding exciton model of dimers. The results are used to calculate theoretical absorption spectra which are compared with those obtained from previous vibronic exciton theories.