The electron paramagnetic resonance (EPR) parameters (g factors gi and
the hyperfine structure constants Ai, i=x,y,z) are
interpreted by using the perturbation formulae for a 3d9 ion in
rhombically ({D}2h) elongated octahedra. In the calculated formulae, the
crystal field parameters are set up from the superposition model, and the
contribution to the EPR parameters from the admixture of d-orbitals in the
ground state wave function of the Cu2+ ion was taken into account. Based
on the calculation, local structural parameters of the impurity Cu2+
center in Cd2(NH4)2(SO4)3 (CAS) crystal were obtained
(i.e., Rx≈2.05 {\AA}, Ry≈1.91 {\AA},
Rz≈2.32 {\AA}). The theoretical EPR parameters based on the
above Cu2+-O2− bond lengths in CAS crystal show a good agreement with
the observed values. The results are discussed.Comment: 5 page