Approximate first-order trigonal crystal-field-split energy levels are derived and fitted theoretically for the Sm<sup>3+</sup>-in-CaF<sub>2</sub> (Type I) <sup>6</sup><i>H</i><sub>7/2</sub>, <sup>6</sup><i>H</i><sub>9/2</sub>, and <sup>6</sup><i>H</i><sub>11/2</sub> states of the ground multiplet involved in fluorescence. Crystal-field theory and the Stevens method are employed in this derivation. The resulting energy deviation between the first-order theoretical levels and the empirically derived levels is within 42 cm<sup>-1</sup> for 14 of the 15 levels involved under the assumption of a constancy of the six trigonal crystal-field parameters. Tables are given of the resulting approximate values of the crystal-field parameters, level energies, and eigenfunctions.
NORMAN RABBINER, "Trigonal Crystal-Field Energy Levels of Sm3+ in CaF2 (Type 1)," J. Opt. Soc. Am. 59, 588-590 (1969)