Electronic spectra of Cu2+ and Fe2+ square planar co-ordinated by oxygen in BaXSi4O10

Abstract

The absorption spectrum of copper in the synthetic silicate BaCuSi₄O₁₀ has been measured in the region 4000–22,000 Å. The spectrum can be interpreted by supposing that the order of increasing energy of the 3d orbitals of the copper is d_z² < d_xz,yz < d_xy < d_x²–y². The interpretation is supported by quantitative comparison of the spectra of BaCuSi₄O₁₀ and BaFeSi₄O₁₀(gillespite). A general picture of the electronic structure of the transition-metal ion in the gillespite structure is presented. The ⁵A_1g→⁵E_g transition in BaFeSi₄O₁₀ is briefly discussed.