CRYSTAL-FIELD ENERGY-LEVEL SCHEME OF ER3+ IN GDOCL PARAMETRIC ANALYSIS

The optical absorption spectra of the trivalent erbium ion (Er3+) in p olycrystalline GdOCl (x(Er)=0.09) samples were measured from 200 to 16 50:nm selected temperatures between 9 and 300 K. The luminescence from the S-4(3/2) and F-4(9/2) levels in GdOCl : Er3+ (x(Er)=0.02) was als o observed at 77 K under argon-ion laser excitation in the region betw een 540 and 870 nm. The interpretation of the absorption and emission spectra yielded an energy level scheme consisting of 17(2S+1)L(J) leve ls; i.e. 61 Stark components out of the 182 Kramers doublets for the 4 f(11) configuration. This scheme was fit to a Hamiltonian of 19 adjust able parameters including the free ion [Racah (E0-3), Trees (alpha, be ta, gamma) and Judd (T-k; k=2-4, 6-8) parameters as well as the spin-o rbit coupling constant (zeta(4f))] together with the crystal field B-q (k) (B-0(2), B-0(4), B-4(4), B-0(6) and B-4(6)) parameters according t o the C-4v point group symmetry of the Er3+ Site in the tetragonal lan thanide (Ln) oxychloride. The experimental energy level scheme was rep roduced with a satisfactory root-mean-square deviation equal to 19 cm( -1). The present results were found consistent with the energy level p arametrisation of Pr3+ (4f(2)) in PrOCl, Nd3+ (4f(3)) in NdOCl, Tb3+ ( 4f(8)) in TbOCl as well as of Eu3+ (4f(6)) and Tm3+ (4f(12)) in GdOCl. The influence of the nuclear charge, the energy of the 5s (and 5d) or bitals and the two-electron crystal held terms are discussed as possib le interactions responsible for the evolution of the B-q(k) parameters along the Ln series.