Appl. Magn. Reson. 30, 175- 184 (2006) Applied Magnetic Resonance 9 Springer-Verlag 2006 Printed in Austria EPR of Pb 3+ ion in LiBaF 3 crystals L. K. Aminov, D. G. Zverev, G.V. Mamin, S. I. Nikitin, N. I. Silkin, R. V. Yusupov, and A.A. Shakhov Kazan State University, Kazan, Russian Federation Received December 20, 2005; revised April 5, 2006 Abstract. Complex EPR spectra of paramagnetic centers Pb3+ formed in LiBaF3:Pb 2+ crystals under X-ray irradiation are studied in the temperature range of 10-150 K, It is shown that lead ions sub- stitute Ba2+ ions in the LiBaF3 crystal and are in the cubic-octahedral 12-fold environment of the fluorine ions. The hyperfine structure constants describing the observed spectrum are determined and parameters of superhyperfine interaction with the nearest fluorine ions are estimated. 1 Introduction Crystals doped with mercury-type ns 2 ions such as TI +, Pb 2+, and Bi 3+ are clas- sical model objects in solid-state physics [1, 2]. These crystals are of interest for practical applications due to their usage as scintillators and active materials of solid-state tunable lasers [3]. The properties of the ns z ions have been mainly investigated in alkali halide crystals and crystals with the fluorite structure in which the substituting ion is situated either in the sixfold octahedral or eight- fold cubic environment. Recently the optical properties of crystals with the 12- fold coordination of the substituting ion, such as KZnF3:T1 +, and KMgF3:TI § [4-6] were studied. Luminescence properties of doped perovskites considerably differ from those of alkali halides and fluorites. In this paper we study the LiBaF3:Pb 3+ crystal. LiBaF 3 crystals have a so- called antiperovskite structure (Fig. 1). Ions of the divalent barium are in the 12-fold coordination of the F- ions, while in the crystals with the perovskite- type structure they have the sixfold octahedral position. Pure LiBaF 3 crystals are used as detectors of neutron and gamma radiation [7]. It is proposed that active media for the solid-state tunable lasers may be created on the basis of these crys- tals doped with mercury-type ions. Our studies of the absorption and excitation spectra in LiBaF 3 crystals doped with lead ions have shown the presence of two different centers, both due to the Pb 2+ ions [8]. These centers essentially differ in band intensity and lumines-