Inhomogeneous Broadening: Symmetry of Centers and Disorder in Solid Solutions and Nanocrystals

Abstract

Zero-phonon electronic transitions of Cr³⁺ impurity ions in solid solutions and nanocrystals are studied. In the series of Lu_3xY_3-3xAl₅O₁₂ (0<x<1) garnet solid solution crystals the modification of zero-phonon R-line (²E–⁴A₂) fluorescence spectra of Cr³⁺ ions with changing x occurs in a discrete fashion and is not accompanied by strong inhomogeneous broadening. The effect is ascribed to high C_3i symmetry of Cr³⁺(Al³⁺) sites. The fluorescence line narrowing experiments were performed for the inhomogeneously-broadened R-line of cubic Cr³⁺ centers in MgO nanocrystals. The inhomogeneous broadening in nanocrystals is attributed to spatial confinement.