Paramagnetic Resonance of the Tripositive Curium Ion in Ethylsulfate and Trichloride Crystals

The paramagnetic resonance of the ion Cm³⁺ has been studied by incorporating various amounts of curium in crystals of lanthanum ethylsulfate and anhydrous lanthanum trichloride. For the ethylsulfate crystals, a single line was observed at helium temperatures, characterized by gII=1.925±0.002 and g_⊥=7.73±0.02. A similar line, for which gII=1.925±0.002 and g_⊥=7.67±0.02, occurs for the trichloride crystals. These lines are interpreted as corresponding to transitions within the lowest doublet of the ground level 5f⁷⁸S7/2, which, owing to the high degree of intermediate coupling, does not possess the extremely small splitting typical of S states. The Land\'e g value of the ground level is found to be 1.925. Previous experimental results on the paramagnetic resonance of Cm³⁺, which were difficult to account for theoretically, are shown to be spurious; evidently the reported spectra should have been ascribed to Gd³⁺.