Energy levels of Tm³⁺in yttrium aluminium garnet

Abstract

An improved energy level diagram for Tm3+(4f12) ions in dodecahedral (D2 symmetry) sites in Y3Al5O12 (YAG) has been obtained from experimental absorption and emission spectra. Interferences in line assignment from the spectra of minority perturbed Tm3+ centres or due to electron-phonon interaction are discussed. A parametrized Hamiltonian that includes one-electron crystal-field interactions for D2 symmetry has been used to fit the experimental data. The RMS deviation between 70 experimentally determined levels (from the total of 90) and calculated levels is 9 cm-1 and the individual misfit is no larger than 20 cm-1 The analysis is based not only on the experimentally located energy levels, but also on the information concerning the symmetry labels for Stark levels. The obtained set of crystal-field parameters seems more suitable than the previously reported description of Tm3+ crystal-field energy levels in YAG.