VO2+ and X-Ray Produced V2+ in Tutton Salt

Abstract

The electron spin resonance spectrum of the vanadyl ion (VO2+) in single crystals of Zn (NH4)2(SO4)2·6H2O is studied and the properties of x-ray produced V2+ are compared to those of the V2+ grown directly into the same host lattice. In the unirradiated samples the V–O axis is found to have three possible orientations with populations in the ratio 20:5:1. For the most populous position the spin Hamiltonian parameters at X band are S=½, gx=1.9813, gy=1.9801, gz=1.9331, Ax=0.007120/cm, Ay=0.007244/cm, Az=0.018281/cm, and Q′=7×10—5/cm with the x, y principal axes of the g and A tensor being displaced from each other by 23°20′. Furthermore, the vanadyl hyperfine lines show an additional anisotropic structure of five lines, absent in deuterated samples. The parameters for V2+ at K band in both the as-grown and irradiated crystals are S=3/2, gz=1.9717, gy=1.9733, D=—0.15613/cm, E=—0.02280/cm, and A=—0.00825/cm. A study of the effect of x-ray dose upon the line intensity is made. An impurity model of a vanadyl pentahydrate complex associated with a water moleculy vacancy is proposed.