Optical and E P R spectra of LiNbO, single crystal doped with copper ions are measured in the range of 200 to 6000 nm and in the X-band, respectively. In the temperature range 60 to 200 K a transition is observed from the low-temperature E P R spectra with C, symmetry (gz = 2.403, gn, = 2.121, g, = 2.095 and x^c, = 51") to the high-temperature spectrum with Csv symmetry (g;l = 2.22, g ; = 2.17 and x 11 C,) whose parameters are given by the average of the corresponding parameters of the low-temperature spectra. E P R spectra of LiNbO,: Cu2+ are interpreted taking account of the static Jahn-Teller effect in trigonal field and formation of non-equivalent minima on the adiabatic potential surface. I n case of the static Jahn-Teller effect in trigonal field formulas for the g-factors of d9 ions are derived theoretically. A new model of Cu2+ substitution in LiNbO,, i.e. formation of a CUET-VL~ complex, is suggested. In optical spectra a n absorption band a t 5000 cm-' is detected due to Jahn-Teller splitting of the zEtr ground state. The Jahn-Teller stabilization energy EJT = 1250 cm-l and crystal field parameters 1ODq = 8200 cm-l, w = -1200 cm-l, and w' = 600 cm-l are determined. Tennepa. HpennomeHa HoBaH Monenb a a~e w e~~~ Cu2+ B LiNbO, -06pa30BaHIIe IFOMnJIeKcoB CUiT-VLi. B cneIcTpax OnTLZYecKoro nornoueHHR 06HapyXeHa nonoca Ha TxacToTe 5000 cm-l 06yCfiOBneHHaR FIT pacwennemeM OcHoBHoro YPOBHR 2Eg. Onpeaenemi BH~PTIIFI FIT c~a611n113aq~~ EJT = 1250 cm-l A napaiweTpb1 KpncTannwxecKoro nonrl: 10Dq = 8200 cm-l, TJ = -1200 cm-l, w' = 600 cm-l.

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