Knowledge Bank

The electronic absorption spectrum of $Co2+$ in a site having fourfold coordination is of current theoretical interest. There are many possibilities for sites with coordination number 4, and a study of one, the $CoCl4-$ configuration in three different crystal environments: $Cs2Zn(Co)Cl4$, $[N(CH3)4]2Zn(Co)Cl4$ and $[QH+]2Zn(Co)Cl4$ (Q=quinoline), has been made. The spectra of these crystals have been measured at various temperatures down to $4\circ K$ in polarized light at high resolution, and detailed analyses of the spectra will be reported, as well as a comparison between the observed levels and those predicted by crystal field theory for a site of pure tetrahedral symmetry