EPR and optical spectroscopy of Yb3+ ions in CaF2and SrF2

The Yb 3+ paramagnetic center of the trigonal symmetry (oxygen paramagnetic center T 2 ) in CaF 2 and SrF 2 single crystals is studied by EPR and optical spectroscopy. The Stark level energies of the Yb 3+ multiplets are established from absorption, luminescence and excitation luminescence spectra and the crystal field parameters are calculated.