EPR and Optical‐Absorption Studies of Cu 2+ ‐Doped Mg(CH 3 COO) 2 · 4H 2 O Single Crystal

X‐band EPR measurements on a single crystal of Cu 2+ ‐doped magnesium acetate tetrahydrate, Mg(CH 3 COO) 2 · 4H 2 O, are made at 295, 77, and 4.2 K. The Cu 2+ spin‐Hamiltonian parameters are evaluated, at all these temperatures, from the EPR line positions by means of a rigorous leastsquares fitting method. The principal values of the g 2 and A 2 tensors indicate that the local symmetry of the Cu 2+ ion, in the host lattice of Mg(CH 3 COO) 2 · 4H 2 O crystal, is tetragonal. The room‐temperature optical‐absorption spectrum, recorded in the 190 to 820 nm wavelength range, is exploited to study the crystal‐field and charge‐transfer transitions of the Cu 2+ ion. On the other hand, both the room‐temperature optical‐absorption and EPR data are used to estimate the core polarization contribution (K) and the molecular‐orbital coefficients for the Cu 2+ ion doping Mg(CH 3 COO) 2 · 4H 2 O.