Applications of resonant cross-relaxation studies in thermally detected EPR

Abstract

An account is given of results obtained from thermally detected EPR experiments on doped rubies under conditions favourable for resonant cross-relaxation effects. From measurements of the signal intensity, known (Cr⁴⁺, Fe²⁺ and V³⁺) impurities and unknown impurities have been studied. The results obtained from Cr⁴⁺ are used to explain the apparent shift of the Cr⁴⁺ resonance observed in previous direct relaxation measurements. A comparison of these results with those from Fe²⁺ and V³⁺ show that the resonant cross-relaxation probability is dependent upon random internal strain. The use of the relaxation properties in this technique is also discussed as an aid in the identification of strongly coupled ions present in very low concentrations.