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 NiI2–4. 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.