Effect of Configuration Interaction of Rare-Earth Ion States on the Intensity of Intermultiplet Transitions

Abstract

We present the analysis of wave functions and the effect of configuration interaction on the intensity of absorption bands for Pr3+, Tm3+, and Er3+ ions. It is shown that due to the strong spin–orbit interaction the wave functions of rare-earth ions are multicomponent superpositions of ″pure″ 2S+1LJ multiplets with different values of S and L and the same values of the angular momentum J. For this reason, the effect of configurational interaction depends not only on the energy gap up to excited configurations, but also on the presence of high-energy 2S+1LJ components. The presence of such components yields a strong influence on the configuration interaction even at the deep layers. Another consequence of the multicomponent composition of the wave functions is the formation of groups of strongly interrelated states. When the configuration interaction is not fully taken into account, the error in describing the oscillator strengths is distributed among all the states of the group, and the low overall accuracy of the description is not perceived as a contradiction to the theory. To confirm the proposed assumptions, the oscillator strengths of the absorption transitions of laser materials activated by Pr3+, Tm3+, and Er3+ ions are described using the modified Judd–Ofelt theory.