Electron spin resonance of 153Eu2+ and 151Eu2+ in RbCl

According to Rubio et al., doped Eu2+ ions took the place of Rb+ ion in RbCl, while Kawano et al. showed that the ions occupied the positions off Rb+ ion site along [111] direction. After Bridgman method, we made the crystal under various conditions. Angular dependence of the ESR spectrum on magnetic field and variation of the line width with temperature were measured. The results proved that the Eu2+ ion occupies a Rb+ site. The obtained values of activation energy of the vacancy in NaCl, KCl and RbCl are 0.41, 0.34 and 0.32 eV, respectively. The spin Hamiltonian parameters for isolated 151Eu2+ ions are as follows; g = 1.991, A = -31.0 x 10-4 cm-1 in KCl and g = 1.991, A = -31.0 x 10-4cm-1 in RbCl. Those for 153Eu2+ in NaCl are 1.995 and -13.0 x 10-4 cm-1. (author)