Response of hybridized (mixed valence) systems to external probes

Abstract

The problem of the response of a hybridized system to an external probe is discussed from a completely quantum-mechanical point of view. An exactly soluble model, which describes qualitatively the mixed-valence states of rare-earth compound solids, is presented. We show that it is possible to obtain regimes of "single response"—e.g., isomer shifts—as well as regimes of "two responses"—e.g., photoelectron emission spectra. The calculation does not involve real time fluctuations. We point out that it would be worthwhile to investigate experimentally intermediate regimes where the characteristic energy of the probe is comparable to the energy separation of the hybridized states.