HYPERFINE-STRUCTURE OF EPR-SPECTRA OF RHOMBIC BINUCLEAR EXCHANGE CLUSTERS IN TRIPLET-STATE

The hyperfine electron-nuclear interaction in antiferromagnetic rhombic binuclear exchange clusters in the triplet state (S = 1) is considered. The second-order corrections to the hyperfine energy levels and the probabilities of allowed (Delta M = 1, Delta m(1) + Delta m(2) = 0) and different types of ''forbidden'' (Delta M = 1, 2; Delta m(1) + Delta m(2) = 0, 1, 2) EPR transitions for canonical orientations of the external magnetic field are calculated. It is shown that the relative line intensities of ''parallel'' low- and high-field fine transitions depend on the parameter of rhombicity Ei. The hyperfine structure of the low-field transition is predicted to be equally spaced. The EPR spectra of {Cu[(CH3)(2)CHCOO](2) . 0.5C(4)H(8)O(2))(2) single crystals were studied and explained on the basis of the calculated results obtained. (C) 1994 Academic Press, Inc.