Structural, Electrical And Percolation Threshold Study Of

A formal approach to deal with the vibronic intensity features in both absorption and emis-sion is put forwarded with reference to the stoichiometric elpasolite type systems. We focus our attention upon both, the electronic and the vibration factors upon which the intensity may be derived from, as well as the details of the coupling between the internal and the external normal modes of vibrations. We introduce a generalized approach to rationalize on a quan-titative basis the observed spectral intensity features in highly relativist features. Our models are intended to avoid any unnecessary parameterization and therefore to reduce the mathemat-ical complications along with, the well known fact that the experimental basis set is always incomplete so that any supra parameterization of the vibronic intensity problems seems to be unrealistic. The advantages and disadvantages of our model calculation are illustrated with reference to several excitations in a number of elpasolites. New trends in the vibronic cou-pling theory are also discussed with reference to systems such as Cs2NaSmCl6, Cs2NaEuCl