Resonance induced divalent Eu states in EuF3 ultrathin layer

Resonant photoemission was used to investigate the EuF3 ultrathin layer for the photon energies within the Eu 4d → 4f excitation region. Photoemission from the valence band in resonance showed the lines which can be attributed to two Eu valence states (Eu+3 and Eu+2) whereas the off resonance spectra of EuF3 ultrathin layer do not exhibit divalent states of Eu. An explanation of that effect is proposed which is based on the charge transfer from the ligand.