ESR Study of X-Ray Irradiated Crystals of Copper Acetate Monohydrate

Abstract

Two single crystals of copper acetate monohydrate were irradiated by x rays at 80° and 290°K, respectively. In the paramagnetic centers produced at both temperatures, a single copper nucleus was found to contribute to the hyperfine structure. Spin Hamiltonian parameters of ⁶³Cu of the center produced at 80° were determined to be $g_z{\text{\hspace{0.17em}=\hspace{0.17em}2.364, g}}_x{\text{\hspace{0.17em}=\hspace{0.17em}2.047, g}}_y{\text{\hspace{0.17em}=\hspace{0.17em}2.086, A}}_z{\text{\hspace{0.17em}=\hspace{0.17em}−\hspace{0.17em}126.8, A}}_x{\text{\hspace{0.17em}=\hspace{0.17em}32.1, A}}_y\text{\hspace{0.17em}=\hspace{0.17em}−\hspace{0.17em}11.3,}\mathrm{and}\text{Q\hspace{0.17em}=\hspace{0.17em}7.3}$ , and those for the center produced at 290°K to be $g_z{\text{\hspace{0.17em}=\hspace{0.17em}2.387, g}}_x{\text{\hspace{0.17em}=\hspace{0.17em}2.069, g}}_y{\text{\hspace{0.17em}=\hspace{0.17em}2.062, A}}_z{\text{\hspace{0.17em}=\hspace{0.17em}−\hspace{0.17em}131.4, |\hspace{0.17em}A}}_x{\text{\hspace{0.17em}|\hspace{0.17em}=\hspace{0.17em}7.0, |\hspace{0.17em}A}}_y\text{\hspace{0.17em}|\hspace{0.17em}=\hspace{0.17em}5.0,}\mathrm{and}\text{Q\hspace{0.17em}=\hspace{0.17em}9.0}$ , the $A$ and $Q$ tensors being given in units of 10⁻⁴ cm⁻¹. The result was compared with that of zinc‐doped copper acetate and was interpreted in terms of molecular orbitals between copper and acetate oxygens. A small mixing of the $d_z^2$ orbital to the ground $d_{x^2{\mathrm{-y}}^2}$ orbital was shown to account for the large anisotropies of both the $g$ tensor and $A$ tensor for the sample irradiated at 80°K. The paramagnetic center produced at 80°K was converted irreversibly at about 150°K to another species, which was found to be identical to that produced at 290°K.