PARAMETRIC ANALYSIS OF THE ENERGY-LEVEL SCHEME OF PR3+ IN LA2O2CN2

The energy level scheme of Pr3+ was studied in lanthanum oxycyanamide, La2O2CN2. The UV-vis-NTR absorption spectra of Pr3+ were measured bet ween 10 and 150 K and the luminescence spectrum at 77 K. The complete 4f(2) electron configuration of Pr3+ (91 levels) was simulated by a ph enomenological model including eight refinable free ion and nine cryst al field (c.f.) parameters. A total lack of energy level degeneracy wa s observed indicating that the La3+ site symmetry cannot be higher tha n C-2n. Because of a close structural relation to the tetragonal rare earth (RE) oxychlorides, REOCl, the simulation was carried out accordi ng to the C-4v-->C-2v descending symmetry method. The initial C-4v sym metry required five non-zero c.f. parameters, while the lowering to C- 2v eventually introduced four additional ones. The 31 experimental ene rgy levels were reproduced with a satisfactory rms deviation of 18 cm( -1). No major discrepancies between the two energy level sets were obs erved. The four additional c.f. parameters for the C-2v symmetry assum ed low values indicating only a minor deviation from C-4v. The results are consistent with those obtained earlier for La2O2CN2:Eu3+. (C) 199 8 Elsevier Science B.V. All rights reserved.