High-resolution polarized absorption and fluorescence spectra of ${\mathrm{Pr}}^{3+}$ in LiY${\mathrm{F}}_4$ were measured at temperatures between 10 and 300°K. Energy-level assignments were made assuming electric-dipole transition selection rules for $S_4$ site symmetry. Forty-six energy levels of the $4f^2$ ground configuration were established, including 44 in the lowest nine multiplets. Crystal-field parameters were determined that gave a rms deviation of 15.8 ${\mathrm{cm}}^{-1\mathrm{}}$ between 41 of the experimental energy levels and calculated values. The parameters were $B_{20}=488.9\mathrm{}$, $B_{40}=-1043\mathrm{}$, $B_{44}=1242\mathrm{}$, $B_{60}=-42\mathrm{}$, Re $B_{64}=1213\mathrm{}$, and Im $B_{64}=22.5\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$. These parameters were used to obtain the remaining energy levels, yielding a complete energy-level scheme for the $4f^2$ configuration of ${\mathrm{Pr}}^{3+}$. The crystal-field parameters for ${\mathrm{Pr}}^{3+}$ in LiY${\mathrm{F}}_4$ were compared to those for other ions in this host. A theoretical calculation of line intensities was performed in which the odd-fold crystal-field parameters were obtained from a lattice sum. Line intensities were measured and compared with theory.

• Received 6 July 1978

DOI:https://doi.org/10.1103/PhysRevB.19.6442