Measurement and crystal field analysis of energy levels of Ho3+ and Er3+ in KGd(WO4)(2) single crystal

Optical absorption and photoluminescence spectra performed on Ho3+ (4f(10)) and Er3+ (4f(11)) doped KGd(WO4)(2) single crystals were measured at selec ted temperatures between 5 and 80 K. In this monoclinic matrix. space group C2/c (No. 15) the lanthanide ions replacing Gd3+ occupy a single crystallo graphic site with symmetry C-2. The interpretation of these spectra and the simulation of the splitting of L-2S+1(J) levels were carried out in the fr ame of the phenomenological single-electron crystal field theory, through t he simultaneous diagonalization of the energy matrices of the free-ion (fi) and crystal field (cf) interactions. A total of 20 fi and 14 cf adjustable parameters were considered for the reproduction of experimental energy lev els and their associated wavefunctions. The simulated energy level series a re in excellent accordance with the experimental data. i.e. rms deviations, sigma =14.5 and 15.6 cm(-1) for Ho3+ and Er3+, respectively. The compariso n with similar results for Pr3+. (4f(2)) and Nd3+ (4f(3)) allowed establish ment of the variation trends of the cf parameters with the number of 4f ele ctrons. (C) 2001 Elsevier Science B.V. All rights reserved.