Crystal-Field Parameters of Mn~2+ in Mg_2 SiO_4:Mn~2+, Mg_5(SiO_4)_2F_2:Mn~2+, and Mg_2SiO_4·MgF_2:Mn~2+

摘要

Individual bands in the excitation spectra of Mn~2+-activated magnesium silicates and fluorosilicates were identified. The observed bad positions were used to calculate the crystal-field parameters B, C, an Dq in the weak-field approximation and the energies of excited states. The calculation results were found to be in reasonable agreement with experiment. The decrease in the degree of covalent bonding is accompanied by an increase in B and decrease in Dq on going from Mg_2SiO_4 to Mg_5(SiO_4)_2F_2 and Mg_2SiO_4·MgF_2, in accor- dance with the position of the O~2- and F~- ions in the nepheloauxetic and spectrochemical series.