EPR of VO 2+-doped CdK 2(SO 4) 2·6H 2O: Forbidden hyperfine transitions and bonding coefficients

Abstract

Extensive room temperature X-band EPR measurements on a single crystal of VO 2+-doped CdK 2(SO 4) 2·6H 2O have been carried out. In addition to the allowed transitions, strong nominally forbidden hyperfine transitions were observed. The intensities of the allowed and forbidden hyperfine lines have been well accounted for theoretically to be due to the hyperfine interaction, S·Ã·I . The principal values and direction cosines of the principal axes of the g̃ 2 and à 2 tensors of VO 2+, as well as the principal values and direction cosines of the principal axes of the quadrupole tensor, Q̃ , of VO 2+, are evaluated using least-squares fitting procedures from the allowed and forbidden hyperfine line positions, respectively. The asymmetry parameter for the vanadium nucleus has been estimated to be 0.78. The orientation of the VO 2+ molecule (V 4+−O 2− bond) has been determined to lie close to the Cd−H 2O(8) direction. Finally, using the experimental optical-absorption data previously reported and the present EPR data the bonding coefficients of the VO(H 2O) 2+ 5 complex have been estimated.