Vibrational exciton Hamiltonian energies

The two-exciton manifold consists of two types of doubly excited vibrational states. The first are overtones (local), where a single bond is doubly excited. The other are collective (nonlocal), where two bonds are simultaneously excited (43,50). We denote the former OTE (overtone two-excitation) and the latter CTE (collective two-excitation). A pentapeptide has 5 OTE and 10 CTE. The two-exciton energies are determined by the parameters gn in the Hamiltonian [Equation (17)], which in turn depend on the peptide group energies G , the anharmonicity An, and dipole moment ratio Kn, n = l,...,5. We set them equal for all CO units... 

Another significant source of variations in the local site energies of molecular ions and excitons in condensed media is the modulation of these energies by the thermal vibrations either of the medium (e.g., acoustical phonons and librons) or of the molecular ion (exciton) itself (intramolecular vibrations). A model Hamiltonian which incorporates electronic interactions with... 

---