Farbeffekte in oxidischen and anderen Mn2+-Verbindungen – die Ligandenfeldspektren von MgO/MnO- und CaO/MnO-Mischkristallen sowie von MnAl2O4

Colour Effects in Oxidic and Other Mn²⁺ Compounds – the Ligand Field Spectra of Mixed Crystals MgO/MnO, CaO/MnO, and of MnAl₂O₄ The colour intensity and the shift of the hue is examined for mixed crystals Mg_1?xMn_x^IIO and Mn_1?y^IICa_yO in dependence of the Mn²⁺-concentration and interpreted in terms of Mn²⁺? Mn²⁺ pair interactions and variations of the Mn? O bond length, respectively. The experimental band positions (sextet-quartet transitions) could be fitted quantitatively – also in case of Mn²⁺ in tetrahedral (MnAl₂O₄) and dodecahedral oxygen coordination (Mn₃Al₂Ge₃O₁₂, MnY₂Mg₂Ge₃O₁₂) – by means of crystal field calculations. The obtained ligand field parameters are discussed in comparison with data for octahedral Mn²⁺ ions with H₂O, F^? and Cl^? as ligands.