Electron paramagnetic resonance and optical spectroscopic studies were made of the trigonal paramagnetic Yb3+ ion (so-called O paramagnetic center). The energy levels of the center were deduced from its optical spectra, and the crystal field parameters were calculated.

EPR and Optical Spectroscopy of SrF2 Doped with Yb3+. M.L.Falin, K.I.Gerasimov, A.M.Leushin, H.Bill, D.Lovy, T.Sanadze: Journal of Alloys and Compounds, 2001, 323-324, 692-5