Reactions in Crystalline Lattices: Spectroscopic Evidence for the Oxidation of Sm2+ to Sm3+ in KCl

With varying concentrations of O₂ and H₂O, oxidation of Sm²⁺ to Sm³⁺ is observed. Experimental proof of the oxidation process is given by: (1) the disappearance of the characteristic absorption bands of Sm²⁺, accompanied by a dramatic decrease in the Sm^{2+ 5}D₀→⁷F_J fluorescence intensity; (2) the observation of the ⁵H_5/2→⁴I_13/2 absorption lines of Sm³⁺; and (3) the reappearance of Sm²⁺ fluorescence lines upon gamma irradiation of the oxidized sample. The discovery of a cubic Sm²⁺ site, which gives rise to a ⁵D₀→⁷F₁ fluorescence transition with a magnetic splitting factor of $\text{1.48 ± 0.05}$ in excellent agreement with the Landé gλ factor of 1.5, is also reported. The significance of the hitherto unobserved cubic site is discussed.