ANALYSIS OF CORRELATION-EFFECTS IN THE CRYSTAL-FIELD SPLITTING OF ND3+LACL3 UNDER PRESSURE

Spectroscopic data for Nd3+:LaCl3 at pressures up to 10 GPa are analyzed using a Hamiltonian containing one-electron crystal-field and two-electron correlation crystal-field operators. We find that the ratio of the correlation crystal-field parameter G10A0(4) to the crystal-field parameter B-0(4) decreases from -0.9 at ambient pressure to -0.2 at 10 Gpa. This decrease is explained using the superposition model and the measured changes of the structural parameters under pressure. Our analysis suggests that the dependence of the correlation crystal-field interactions on the Nd3+-Cl- distance is much greater than the distance dependence of the one-electron crystal-field interactions.