Optical absorption properties of ZnF2-RO-TeO2 (R = Pb, Cd and Zn) glasses doped with chromium (III): Neuhauser model and crystal field study

Abstract

Abstract Tellurite glasses with composition ZnF2-RO-TeO2 (R = Pb, Cd and Zn) containing 0.2 wt % of transition metal ions Cr3+ have been investigated for their structural and optical properties. The absorption spectra recorded for Cr3+-doped tellurite glasses indicate an octahedral coordination for the Cr3+ ions. These spectra show distinct features on the 4T2g(4F) absorption band due to the interaction of the 2Eg(2G) and 2T1g(2G) sharp levels with the vibrationally broadened 4T2g(4F) quasi-continuum via spin-orbit coupling called interference dips. This work analyz65es the dips using Neuhauser model in order to give a precisely values of the experimental energy levels of the broad band 4T2g(4F) and of the two 2Eg(2G) and 2T1g(2G) sharp levels. This analysis explains well the notion and the origin of the interference dips observed generally on the absorption spectra of the glasses. The parameters obtained from the Neuhauser model leads to information on the structure of the three glasses. From the experimental energy levels obtained by Neuhauser model, we examine a detailed crystal-field analysis of the visible lines associated to the transitions between the energy levels of Cr3+-doped tellurite glasses. The theoretical study is based on the Racah tensor algebra methods and leads to the electronic structure of the Cr3+ in the three glasses. As a result, Racah and crystal-field parameters have been reliably obtained and permit us to compare the intensity of the crystal field strength environment of Cr3+ in the three glasses. A good agreement between the theoretical and the experimental energy levels are obtained. The results of this work are compared with homolog glasses.