The Yb3+ paramagnetic center of the trigonal-symmetry so-called O paramagnetic center, T2, in single crystals was studied by means of electron paramagnetic resonance and optical spectroscopy. The Stark level energies of the Yb3+ multiplets were deduced from absorption, luminescence and excitation luminescence spectra, and the crystal field parameters were calculated.

EPR and Optical Spectroscopy of Yb3+ Ions in CaF2 and SrF2. M.L.Falin, K.I.Gerasimov, V.A.Latypov, A.M.Leushin, H.Bill, D.Lovy: Journal of Luminescence, 2003, 102-103, 239-42