Absorption spectroscopy ofR3+(R=Pr,Nd)ion pairs inCsCdCl3

Abstract

The energy levels of ${R}^{3+}(R=\mathrm{P}\mathrm{r},\mathrm{N}\mathrm{d})$ ions replacing the divalent ${\mathrm{Cd}}^{2+}$ ions in single crystals of ${\mathrm{CsCdCl}}_{3}$ have been investigated by polarized absorption at 10 K. For charge balance, a majority of ${R}^{3+}$ ions in ${\mathrm{CsCdCl}}_{3}$ form pairs with a vacancy associated with it. The analysis reveals that ${R}^{3+}$ pair ions are in two unequal sites which result from two arrangements: (i) with a vacancy in between the two ${R}^{3+}$ ions and (ii) with a vacancy on any one side of the two ${R}^{3+}$ ions. Indeed two types of spectra are observed due to the different ${C}_{3v}$ crystal fields at these two sites. Thirteen levels of ${\mathrm{Pr}}^{3+},$ arising out of five multiplets, and thirty levels of ${\mathrm{Nd}}^{3+},$ arising out of twelve multiplets, have been identified along with their irreducible representations. The best free-ion and crystal-field parameters for ${\mathrm{Pr}}^{3+}$ have also been determined.