EPR OF HOLE-CENTERS IN NONLINEAR LIBO3 CRYSTALS

Results are presented of an EPR study of theO(-) hole center in LiB3O5 (lithium triborate) crystals. Analysis of angular dependences of EPR spectra is used to determine the principal values of the g tensor (g(X X) = 2.032, g(YY) = 2.020, g(ZZ) = 2.007), along with the modulus of t he isotropic part of the A(2) tensor (\A\ = 12.2 G) and the orientatio ns of the principal axes of the paramagnetic O- center. The most proba ble model for the O- center in lithium berate crystals is the followin g: a hole trapped by the center is localized on ap-orbital of an oxyge n ion linking two boron atoms with coordination numbers three and four near a negatively charged stabilizing structural defect. In this case the characteristic hyperfine splitting is due primarily to the intera ction of the unpaired electron spin with the B-11 nucleus. (C) 1997 Am erican Institute of Physics.