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Abstract
X-ray absorption spectroscopy was applied to study the pressure-induced valence changes in EuS and SmTe, which are divalent semiconductors of NaCl-type structure at ambient pressure. In both systems the Eu-LIII and Sm-LIII thresholds exhibit the onset of intermediate valencies of the rare earth ions at 15 GPa and 4 GPa, respectively. In EuS, one observes only a small increase of the valency within the investigated pressure range (36 GPa), while in SmTe a full transition to trivalency is observed above 20 GPa. The transition to the CsCl-Type high-pressure phase has no significant influence on the valence in both systems.