No abstract

It is shown that for every transition in its individual residues, a helix has two transitions whose moments are respectively parallel and perpendicular to the screw axis. The largest contributions to the rotational strengths of these bands are equal and opposite in the two cases. As a result, their net effect on the optical activity contains a term proportional to the interval between the two upper states. This term shows abnormal dispersion and its magnitude and sign are more easily interpreted than any other component of the rotatory power.

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.

The interactions which occur between nuclear and electronic motions in electronically degenerate states of octahedral molecules are investigated.frequency" polarizations of the electronic motions: if V is the electronic Hamiltonian, which difFers from the total Hamiltonian in the absence of the nuclear kinetic energies alone, then