Study of strongly overlapping Rh2+ EPR spectra by high-resolution magnetic resonance techniques

Abstract

Recent EPR and ENDOR publications demonstrated that several closely related Rh²⁺ complexes may be simultaneously present in rhodium doped NaCl and AgCl. These complexes only differ with respect to vacancy compensation. They exhibit strongly overlapping X-band EPR spectra with g_⊥ ≈ 2.5 and g_‖ ≈ 2. In the present study, solution- and melt-grown NaCl single crystals doped with Rh³⁺ were subjected to several treatments, such as X-irradiation, heating and thermal pulse annealing. While X-band EPR alone has insufficient resolution to resolve the spectra of the various rhodium complexes, a combined X-band ENDOR and W-band EPR study allows a consistent spectrum decomposition and interpretation. The X- and W-band Rh²⁺ spectra of both solution- and melt-grown NaCl single crystals are discussed in terms of the same [RhCl₆]²⁻·nvac (n = 0, 1, 2) complexes.