Stark energy levels of Eu 3+ (4f 6 ) ions in CdF 2 -CaF 2 :Eu epitaxial superlattices on Si have been measured by laser spectroscopy and calculated in an exchange charge model. Two types of centre have been considered in the CaF 2 layer: an 'interface centre', close to the CdF 2 /CaF 2 interface, and a 'remote centre' located in the core of a layer. The influence of distortion, created by the silicon substrate, has been taken into consideration. The calculations confirmed a previously suggested 'electron' model of the interface centre.
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