Energy Level Scheme of Nd3+ Ion in Rare Earth Oxyhalides, REOX (X = F, Cl, and Br)

L. Beaurya, J. Hölsäb, J. Korventaustab, J.-C. Krupac, R.-J. Lamminmäkib, P. Porchera, H. Rahialad and E. Säilynojab aC.N.R.S., U.P.R. 209, F-92195 Meudon, France bUniversity of Turku, Department of Chemistry, FIN-20014 Turku, Finland cI.P.N., Laboratoire de Radiochimie, F-91406 Orsay, France dÅbo Akademi University, Department of Chemistry, FIN-20500 Turku, Finland

Received: June 24, 1996

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The energy level schemes of the neodymium oxyhalides (NdOX, X = F, Cl, and Br) were studied and simulated with a phenomenological model accounting simultaneously for both the free ion interactions and the crystal field effect. The former included the electrostatic and interconfigurational interactions as well as the spin-orbit coupling. The simulations were carried out by using the data from the optical absorption and luminescence as well as the inelastic neutron scattering measured at low temperatures between 2.5 and 77 K. The values of the Slater integral F2 describing the electrostatic interactions decrease while F4 and F6 increase as a function of the ionic radius of the halide anion. The strength of the spin-orbit coupling is quite the same in all three matrices. The crystal field effect - measured as the crystal field strength parameter S - is almost twice as strong in the hexagonal NdOF matrix (650 cm-1) than in the tetragonal NdOCI or NdOBr (367 and 378 cm-1, respectively). Similar evolution was obtained for the short-and mid-range crystal field strengths related to the spatial extension of the interaction.

DOI: 10.12693/APhysPolA.90.1203 PACS numbers: 71.55.-i, 71.70.Ch, 78.40.-q, 78.55.-m