Stark energy levels of Eu3+ (4f6) ions in CdF 2-CaF2: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 CaF2 layer: an 'interface centre', close to the CdF2/CaF2 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.