Analysis of the Paramagnetic Resonance and Optical Spectra of d3,7 Ions in Tetragonal Crystal Fields. I. Orbitally Nondegenerate Ground States

The ligand‐field Hamiltonian, including spin–orbit coupling and all states of the configuration, has been diagonalized for the $d^{\text{3,7}}$ ions in tetragonal environments. The g‐tensor components have been determined within the lowest two Kramers doublets in cases where the ground state is orbitally nondegenerate. The variation of $D$ , $\mathrm{g\Vert }$ , and $\mathrm{g\perp }$ with the parameters of the tetragonal potential has been investigated for parameter values appropriate to the Co²⁺ ion in $D_{\text{2d}}$ symmetry. The results are compared with those obtained from simple perturbation expressions which have been used in the literature. Parameters for the extended spin Hamiltonian are evaluated directly. Matrices for the tetragonal potential are used to discuss optical and paramagnetic resonance data for Cs₃CoCl₅ and Co²⁺ in CaF₂. Polarized single‐crystal optical data for Cs₃CoCl₅ at 4.2°K are described for the ${}^4{T}_1{(}^4\mathrm{F)}$ and ${}^4{T}_1{(}^4\mathrm{P)}$ states.