Eu valence in ultra-thin layers of EuF3 derived from photon energy dependent photoemission and photoabsorption

X-ray absorption (XAS) and resonant photoemission (RESPE) have been used to study Eu valence in ultra-thin EuF3 layers grown by MBE. It was shown that resonant photoemission (RESPE) from EuF3 ultra-thin layers exhibits different features for photon energies close to the 4d-4f threshold (130-150 eV) and the 3d-4f excitation region (1120-1170 eV). For the low energy resonance a clear effect of resonance induced Eu2+ states (final state 4f6) has been found whereas no divalent Eu states have been observed when photon energy was tuned to the 3d-4f transition. Our results indicate that Eu valence derived from the XAS and RESPE spectra depends on photon energy and is dominated by the final state effects for the 4d-4f resonance. An explanation is given based on the screening effect and different decay channels of the 4d-4f and 3d-4f resonances.