Abstract
The cause of the split of 4A4E(4G) Mn2+ excited level measured on minerals spectra is discussed. It is our view that ∆E = |4E(4G) − 4A(4G)| should be considered an important spectroscopic parameter. Among the possible reasons for the energy levels splitting taken under consideration, such as the covalent bond theory, the geometric deformation of the coordination polyhedron and the lattice site’s symmetry, the first one was found to be inappropriate. Two studied willemite samples showed that the impurities occur in one of the two available lattice sites differently in both crystals. Moreover, it was revealed that the calculated crystal field Dq parameter can indicate which of the two non-equivalent lattice sites positions in the willemite crystal structure was occupied by Mn2+. The above conclusions were confirmed by X-ray structure measurements. Significant differences were also noted in the Raman spectra of these willemites.
Highlights
Minerals 2021, 11, 1215. https://The luminescence of synthetic materials subsidized with manganese ions, especially (2+), is still intensively researched and has been for many years [1,2]
We present a discussion of the influence of the following factors on the value of ∆E, i.e., (4 E4 A1 (4 G)) splitting—geometric deformation of lattice site, participation of covalent bond and, only qualitatively, a low position symmetry
We present a discussion of the influence of the following factors on the tetrahedra
Summary
The luminescence of synthetic materials subsidized with manganese ions, especially (2+), is still intensively researched and has been for many years [1,2]. Calculation of the energy of excited levels whose orbital degeneracy has been removed due to low symmetry of occupied site or coordination polyhedron is presented as a solution of p the following crystal field Hamiltonian H = ∑ p=2 , ∑4k=− p Bkp ·Okp [15,16]. In the second [19], with changed Bkp parameters, a complete split of energy levels was observed, but the obtained values of parameters B (945 cm−1 ), C (2851 cm−1 ), and Dq (340.5 cm−1 ) are rather not credible Both of the above examples [17,18,19] showed that this method of calculation energy of excited levels of Mn2+ present in a low symmetrical lattice site does not give results consistent with the experimental data. We discuss the possibility of Mn2+ being present in two non-equivalent lattice sites in willemite samples
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