Evaluation of hyperfine and quadrupole tensors from ENDOR measurements on single crystals

Abstract

A method has been developed for evaluating the hyperfine and quadrupole coupling tensors A and Q from ENDOR measurements made on single crystals. The method is applicable even when the tensors do not have common principal axes. An analysis has been made of the modifications required when the first order analysis based on the assumptions that gβB ⪢ G, F and G ⪢ P is not sufficiently accurate. The second order hyperfine energy contribution and the cross product of fine and hyperfine energy contribution of the order FG gβB both cancel when the two frequencies corresponding to the transitions ( M, m) → ( M, m − 1) and (− M, − m) → (− M, − m + 1) are added. P is the quadrupole coupling term. The method has been applied to re-analyze the 14N ENDOR data for NO 2. The principal values of the 14N quadrupole coupling obtained here, namely −0.2, −1.4 and 1.6 MHz, differ significantly from those obtained assuming parallel principal axes for A and Q whereas the hyperfine coupling tensor is the same in the two cases.