Magnetic circular dichroism spectrum of the tetraiodonickelate(II) ion

Abstract

Magnetic circular dichroism (MCD) measurements are reported from 4.2 to 37 K and 7 to 46 kG on crystals of (N(C₂H₅)₄)₂ ZnI₄ doped with NiI^2–₄. The charge transfer absorption and the ligand-field bands arising from transitions from ³T₁(³F) to components of ¹G were examined. From the temperature dependence of the MCD it is concluded that the first order spin-orbit splitting of the ³T₁ ground state is almost completely quenched; the components span no more than about 20 cm^–1, compared with several hundred cm^–1 predicted by simple crystal field theory. The small separations between the excited components of the ground state necessitate consideration of temperature dependent B-term contributions to the MCD. Assignments of the ligand-field transitions are confirmed by linear polarisation measurements. Two possible reasons for the quenching of the ground state multiplet are discussed.