Use of Pseudopotential for Crystal-Field Splitting of J Levels of TmCl3· 6H2O

A method of calculating the crystalline Stark field splitting of J levels for Tm³⁺ in ${\mathrm{TmCl}}_3\text{· 6}{\mathrm{H}}_2\mathrm{O}$ is described which uses the idea of a higher symmetry crystal field. The higher symmetry crystal‐field Hamiltonian is selected by considering the Stark levels within a given J manifold having the same intensity as degenerate. It is found that the calculation is in a coordinate system with the higher symmetry axis perpendicular to the direction of the symmetry axis reported for this crystal. [D. N. Olsen and J. B. Gruber, J. Chem. Phys. 54, 2077 (1971)]. A rotation of the coordinate system is performed to correct for this condition. Finally, the thulium parameters obtained are compared with the parameters for ${\mathrm{HoCl}}_3\text{· 6}{\mathrm{H}}_2\mathrm{O}$ where polarization data were available for identifying individual Stark levels necessary in making a definitive crystal‐field splitting calculation.