Charge resonance and charge transfer interactions in naphthalene homo- and hetero-dimers

Charge resonance interaction in naphthalene homo- and hetero-dimer cations is studied by photodissociation spectroscopy of the charge resonance and the local excitation transitions. The resonance interaction in naphthalene dimer cation is slightly weaker than that of a benzene dimer cation because of partial overlapping of the respective aromatic rings. A local excitation band of the benzene cation chromophore is observed in the spectrum of a naphthalene-benzene hetero-dimer cation at nearly the same position as that of the benzene dimer cation. This indicates that in spite of its higher ionization potential the positive charge stays on the benzene molecule in some probability. On the basis of the band position of the charge resonance transition as well as the intensity of the local excitation band, the probability is analyzed to be approximately 9%. This means 91% is localized on the naphthalene chromophore in this hetero-dimer.