Fine-Tuning the Cr R-Line by Controlling Pauli Antisymmetry Strength.

Fine-tuning of the Cr zero-phonon R-line fluorescence (E-A) has recently been achieved by varying the composition of Cr-doped solid solution garnets. Chemical substitutions of Y with Lu and Tb produce R-line shifts and multiplets that cannot be associated with direct or indirect changes in the Cr-O covalency alone and raise important questions on the nature of the interactions between the CrO active center and its environment, hence on the impact of local disorder. In this Letter we show that Pauli antisymmetry interactions with next-nearest neighbor ions, which are commonly omitted from theoretical analyses, induce a nephelauxetic effect on the CrO active center that shifts the R-line. The strength of these interactions increases with the ionic radius and number of codopant ions, all of it resulting in controlled shifts and multiplets of R-lines. The Pauli antisymmetry induced nephelauxetic effect, combined with the R-line shift with lattice constant, allows for a very fine-tuning of the Cr R-line.