Study of strongly overlapping Rh2+ EPR spectra by high-resolution magnetic resonance techniques
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Kris Sabbe, Henk Vrielinck, Freddy Callens, Etienne Boesman, Hans Vercammen, Hanno Käß, Etienne Goovaerts, August Bouwen and Dirk Schoemaker
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.