Electronic Spectra of Dimers: Derivation of the Fundamental Vibronic Equation

Abstract

The Hamiltonian describing the vibronic states of a dimer formed by two identical molecules is derived. The monomeric units are assumed to couple by resonance forces only and to have different equilibrium positions in the ground and excited states. The competition of these two effects is formulated mathematically. The strong coupling case occurs when the resonance forces dominate; the weak coupling case arises when the effect of the change of equilibrium positions dominates.