Density of states in the gap of a disordered material using E.S.R./optical correlations

Abstract

Abstract Electron-spin-resonance studies of rapidly frozen solutions of alkali metals in anhydrous hexamethylphosphoramide (HMPA) indicate the presence of several, distinct localized electron states. Optical studies of similar species in a variety of fluid solutions reveal a simple correlation between the optical transition energy and the degree of occupation of the alkali-metal ns orbital. From this information we evaluate a distribution function for the various (localized) paramagnetic states present in the low-temperature disordered system. The localized states assume only a few, discrete eigenstates within the host (HMPA) bandgap. We speculate on the possible origin of these states; particular emphasis is placed upon the influence of lone-pair electrons and steric effects in determining the molecular configurations of the host matrix around the alkali atom during the quenching process. We point out the striking similarities between the eigenfunctions/eigenstates of matrix-bound states and the excited ...