Electron Spin Resonance of Tripositive Curium in ThO2and CeO2

Abstract

The ESR spectra of ${}_{}{}^{244}{}_{}{}^{}\mathrm{Cm}_{}^{3+}{}_{}{}^{}$-doped Th${\mathrm{O}}_2$ and Ce${\mathrm{O}}_2$ single crystals were measured at approximately 10 Gc/sec and liquid-helium temperatures. Sites of cubic symmetry were observed in both hosts, with the crystal-field splitting being larger than the microwave quanta used. The ground states are ${\Gamma }_6$ doublets, indicating that the fourth-order parameter of the cubic crystal-field Hamiltonian is negative. For Th${\mathrm{O}}_2$, the $g$ value was 4.484±0.002, and for Ce${\mathrm{O}}_2$, it was 4.475±0.002.