STUDY OF STRONGLY OVERLAPPING RH2-SPECTRA BY HIGH-RESOLUTION MAGNETIC-RESONANCE TECHNIQUES( EPR)

Recent EPR and ENDOR publications demonstrated that several closely re lated Rh2+ complexes may be simultaneously present in rhodium doped Na Cl and AgCl. These complexes only differ with respect to vacancy compe nsation. They exhibit strongly overlapping X-band EPR spectra with g(p erpendicular to) approximate to 2.5 and g(parallel to) approximate to 2. In the present study, solution- and melt-grown NaCl single crystals doped with Rh3+ were subjected to several treatments, such as X-irrad iation, heating and thermal pulse annealing. While X-band EPR alone ha s insufficient resolution to resolve the spectra of the various rhodiu m complexes, a combined X-band ENDOR and W-band EPR study allows a con sistent spectrum decomposition and interpretation. The X- and W-band R h2+ spectra of both solution- and melt-grown NaCl single crystals are discussed in terms of the same [RhCl6](2-).nvac (n = 0, 1, 2) complexe s.