Monocrystalline Rh2+-doped material was studied by using electron paramagnetic resonance and electron nuclear double resonance techniques. An orthorhombic Rh2+ centre was found which was similar to that observed in AgCl, where Rh2+ replaced Na+ to form a [RhCl6]4− complex that was elongated along a [001] axis, with a charge-compensating Na+ vacancy in a second-nearest Na+ position in the equatorial plane. Two further axial Rh2+ centres were found in which the Na+ vacancy was not in the nearby equatorial plane. Interactions with axial second-nearest 23Na and axial 103Rh nuclei could be resolved in the powder ENDOR spectra of NaCl:Rh2+. The powder ENDOR spectra of AgCl:Rh2+, precipitated from aqueous solution, showed that the Rh2+ defect was different to that generated in Rh2+-doped melt-grown AgCl.

EPR and ENDOR Investigation of Single Crystalline and Powdered NaCl:Rh2+ and AgCl:Rh2+. S.Schweizer, J.M.Spaeth: Journal of Physics and Chemistry of Solids, 1997, 58[6], 859-67