Paramagnetic resonance in diluted copper salts III. Theory, and evaluation of the nuclear electric quadrupole moments of 63Cu and 65Cu

The previous theory of Abragam & Pryce (1951) is extended to a special case of rhombic symmetry, and to include higher-order terms. The theory gives satisfactory agreement between the observed anisotropies of the g-tensor and the magnetic hyperfine structure, and shows that the size of the hyperfine structure is about 15 % smaller than would be expected on the assumption that the magnetic electron is confined to the copper ion. Comparison with the optical absorption spectrum suggests that the spin-orbit coupling is reduced by about the same amount, and the effects are explained by an overlap of the wave function of themagnetic electron on to neighbouring water molecules. The nuclear electric quadrupole moments are found to be (in units of 10-24 cm2) ; 63Cu, — 0.16; 65Cu, — 0.15, with an estimated maximum error in the theory of 20 % .