Spectroscopic determination of ion-defect pair energies in KCl:Sm2+

Hitherto undetermined symmetry origins of fluorescence lines occurring in the $\mathrm{KCl}:{{\mathrm{Sm}}^{\text{2+}}}^5{D}_{\text{0→}}^7{F}_5$ transition region are examined in terms of lifetime measurements. From relative intensity measurements of all the dominant lines observed in the entire ${}^5{D}_{\text{0→}}^7{F}_J\text{(0≤ J ≤ 6)}$ fluorescence spectrum and experimentally determined effective equilibrium distribution temperature of 219°K, the binding energies of the nearest‐neighbor [C_2ν(1,1,0)] and next‐nearest‐neighbor [C_4ν(2,0,0)] Sm²⁺−K⁺ vacancy pairs are found to be −0.45 and −0.39 eV, respectively. At ordinary temperatures, the dominant sites, in the order of relative importance, are the C_2ν(1,1,0), C_s(2,1,1), and C_4ν(2,0,0) pairs. This observation is interesting in view of the predominance of the C_4ν(2,0,0) site in the KCl:Sr²⁺ and KCl:Mn²⁺ systems.