Solid state exciton concept

Figure 3a shows several representative photoconductivity excitation spectra in pure xenon Fig. 3b for argon doped by ethane. In pure liquid and solid xenon and krypton, the value of as determined by means of the photoconductivity threshold is in full accord with its value as found from the limit of Wannier-Mott excitonic series (Asaf and Stelnberger, 1974 Laporte et al., 1985 see also below). This fact furnishes independent support for the applicability of solid-state concepts like energy... 

The basic concepts o hich the relaxation-localization model is based are simple. The molecular character of the solid state leads to weak interactions between the molecular entities and hence to a high degree of disorder. Contributions to the disorder are both static (e.g., local variations in composition and/or structure) and dynamic (e.g., thermally induced vibrations) in nature. The static disorder localizes both injected charges as molecular ions and injected excitations as molecular excitons. Once localized, these entities interact strongly with the (dynamic) charges which they induce in the surrounding dielectric medium. The induced charges in turn can be described... 

The local or extended nature of molecular-ion (or exciton) states in molecular solids is determined by a competition between fluctuations in the local site energies of these states (which tend to localize them) and the hopping integrals for inter-site excitation transfer (which tend to delocalize them). In order to define this fluctuation-induced localization concept more precisely, consider the model defined by the one-electron Hamiltonian... 

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