ELECTRON-SPIN-RESONANCE STUDY OF CENTERS FORMED IN GAMMA-IRRADIATED PBCL2 CRYSTALS

An analisis is presented by utilizing the electron spin resonance spec tra of new defects which are produced in PbCl2 single crystals irradia ted at liquid nitrogen temperatures with gamma-rays from a Co-60 sourc e. One of the g tensor axes of the defects corresponds to the crystall ographic c-axis, and the other two make an angle of about 12-degrees w ith the a- and b-axes. The components of the g-factor are g(x) = 1.494 +/- 0.005, g(y) = 1.322 +/- 0.005 and g(z) = 1.662 +/- 0.005. The pri ncipal axes of the hyperfine coupling tensor A are collinear with neit her the g tensor axes nor the crystallographic axes. The resolved hype rfine structure indicates that these defects fit a model of the parama gnetic centers consisting essentially of an electron trapped at paired lead ions, that is, the Pb-2(3+) centers.