EPR STUDIES OF PARAMAGNETIC RHODIUM CENTERS IN LIH AND LID

EPR spectra have been obtained for two independent paramagnetic Rh centers in UV-irradiated single crystals of LiH and LiD. The spin Hamiltonians for both species indicate S = 1/2 and are assigned to Rh2- ions with low-spin 4d 7 electron configurations. Analysis of the anisotropic g-factor for the tetragonal center shows the unpaired electron in the Rh 4d x2-y2 orbital. The unpaired electron occupies the 4d 3z2-r2 orbital in the orthorhombic center. The g factor, hyperfine constants, and protium superhyperfine constants for the Rh centers in LiH and LiD are compared with similar parameters for Rh2+ ions in several halide and oxide crystals. Although the isotropic protium hyperfine values indicate significant ls> -4d> orbital interactions, the total covalency in the Rh-H(D) bonds is rather small since the hydrogen |2p > orbitals cannot participate. The displacements of H ligands in the Rh centers have been determined from the direct-dipolar contributions to the superhyperfine tensor. © 1979 American Institute of Physics.