The electronic spectra of mixed crystals

Abstract

The excited electronic states of dilute mixed crystals are discussed in terms of the theory of intermolecular interactions in dipole-dipole approximation. Resonance interactions of the Davydov type, which are of the first importance in pure crystals, are absent. However, interactions between host and guest molecules are generally of com parable importance to second-order interactions in pure crystals, and lead to similar changes in absolute absorption intensities and polarization ratios. There is a substantial departure from oriented-gas behaviour, which can be regarded as only a rough approximation to mixed crystal properties.