Theory of Mössbauer effect in intermediate-valence compounds.

Abstract

Using a simple microscopic model, we study the response function corresponding to the Mössbauer effect in an intermediate-valence atom. We derive expressions for the spectra which can be used to analyze experimental results at all temperatures, as well as for different hosts in which the intermediate-valence ion maybe embedded. For metallic hosts at high temperatures our theory justifies the use of the expressions previously proposed by Bauminger, Nowik, Ofer, Felner, and Mayer, based on Kubo ’s stochastic theory of line shape. A t low temperatures, where the latter cannot be applied due to the non-Markovian character of the fluctuations, our results allow us to interpret experimental data and to obtain from them the parameters characterizing the intermediate-valence condition. For semiconducting hosts, where the phenomenological stochastic theory does not apply either, we can predict spectra which are consistent with experimental results