EPR and optical spectroscopy of Yb3+ ions in CaF2 and SrF2

Yb3+ paramagnetic center of trigonal symmetry in CaF2 and SrF2 and SrF2 single crystals was studied using electron paramagnetic resonance and optical spectroscopy. Stark level energies of the Yb3+ multiplets were established from absorption, luminescence and excitation luminescence spectra and crystal field parameters were calculated. It was found that the obtained crystal field parameters decreased as the lattice constant increased