Zeeman Anisotropy Fluorescence Spectroscopy, Characteristic Radiative Lifetimes, and Novel Site Symmetries in KCl:Sm2+

By means of Zeeman anisotropy fluorescence (ZAF) and its field dependence (up to 55.8 kG), the authors have investigated the 4.2 K narrow-line fluorescence of KCl:${\mathrm{Sm}}^{2+}$ and identified some hitherto unreported ${\mathrm{Sm}}^{2+}$ sites. The strong no-field line at 7693.5 Å (${}_{}{}^5{}_{}{}^{}D_0^{}{}_{}{}^{}\to {}_{}{}^7{}_{}{}^{}F_3^{}{}_{}{}^{}$) and a very weak no-field line at 8742.8 Å (${}_{}{}^5{}_{}{}^{}D_0^{}{}_{}{}^{}\to {}_{}{}^7{}_{}{}^{}F_5^{}{}_{}{}^{}$) are shown to be of $C_{3v}$ symmetry origin. The 24.5-kG ZAF pattern observed in the 7696-7700-Å (${}_{}{}^5{}_{}{}^{}D_0^{}{}_{}{}^{}\to {}_{}{}^7{}_{}{}^{}F_3^{}{}_{}{}^{}$) region has been identified to originate from a type-II $C_s$ site. The 26.5-kG ZAF patterns of the $C_{3v}$ no-field line at 7693.5 Å and the type-I $C_s$ no-field line at 7694.5 Å overlap in the 7693-7695.3-Å region, and are elucidated through the field dependence of their Zeeman components. Characteristic radiative lifetimes of the ${}_{}{}^5{}_{}{}^{}D_0^{}{}_{}{}^{}$ level in several ${\mathrm{Sm}}^{2+}$ symmetry types have been determined from dominant transitions to the ${}_{}{}^7{}_{}{}^{}F_J^{}{}_{}{}^{}$ ($J<~4$) levels. There are two distinct $C_{4v}$ sites: one with a lifetime of 9.5 msec, and the other 11.2 msec. $C_{2v}$ and type-I $C_s$ sites have lifetimes of 10.5 and 10.8 msec, respectively, which are indistinguishable within the experimental error. The role of ${\mathrm{O}}^{2-}$ compensation of ${\mathrm{Sm}}^{2+}$ in addition to ${\mathrm{K}}^{+}$ vacancy compensation in KCl is discussed in terms of these findings.