CONTRIBUTION OF ORBIT-LATTICE INTERACTION TO SPLITTING OF 8S7/2 GROUND STATE

A calculation of the static contribution of the orbit-lattice interaction to the ground-state splitting of rare-earth S-state ions is made, and the effects of mixing due to spin-orbit coupling are treated explicitly. Both the zero-point and the temperature-dependent phonon contributions are determined, and it is shown that, for Gd3+ in CaF2, the splitting produced by these terms (a) is approximately three orders of magnitude smaller than the measured value, (b) has the opposite sign to the observed splitting, and (c) possesses (by itself) an incorrect temperature behavior. Consequently, in agreement with our initial calculations, which did not include spin-orbit coupling corrections, we conclude that the static orbit-lattice interaction is not responsible for the ground-state splitting of S-state ions. © 1968 The American Physical Society.