PARAELECTRIC RESONANCE OF KCL.LI+

Paraelectric resonance spectra of KCl:Li7+ and KCl:Li6+ are presented for three different frequencies: 63, 24, and 9 GHz. Quantitative results for the case of static electric field E0 [001] support the <111> off-center tunneling model due to Gomez, Bowen, and Krumhansl. We obtain these values for the dipole moment μ and zero-field splitting δ: μ7=μ6=5.6±0.2 D, δ7=0.77±0.03 cm-1, δ6=1.07±0.04 cm-1. These agree with results from several other experimental techniques. Detailed analysis of line shapes and intensities indicates the presence of large random internal strains and of random electric fields. A satisfactory explanation for the presence of these is still lacking. The 63-GHz spectrum for E0 [011] shows a negative resonance (hole") similar to a feature seen previously in ESR experiments on MgO:Ni2+ and MgO:Fe2+. The model of Gomez et al. is shown to satisfy requirements for the occurrence of this negative resonance. © 1969 The American Physical Society."