Optical Spectra and Energy Levels Analysis of the 4fN Ions Doped into Ba2YCl7

Absorption emission and excitation spectra are measured and analyzed to achieve assignments of energy levels for 4f(N) ions in Ba(2)YCl(7):RE(3+) (RE = Pr, Nd, Tb, Dy, Ho, Er, and Tm) crystals. The experimental energy levels were analyzed in terms of the usual free-ion parameters and the crystal field (CF) ones, B(kq), in the Wybourne notation. The orthorhombic C(2v) symmetry is shown to be a good approximation of the actual triclinic C(1) site symmetry at the metal center. The starting values of the CF parameters B(kq) used for fittings for the studied crystals were obtained from superposition model analysis. A good agreement between the calculated and experimental energy levels was obtained with rms deviations in the range from 6.8 cm(-1) (for Ho(3+)) to 14.1 cm(-1) (for Pr(3+)). The fitted sets of B(kq) parameters are, in general, consistent across the 4f(N) series. This study has enabled determination and discussion of the trends in variation of the free-ion parameters and CF ones across the 4f(N) series. The CF parameter set and energy level structure obtained for Nd(3+) ion in Ba(2)YCl(7) crystal are consistent with those for Nd(3+) in structurally related RbY(2)Cl(7) crystal. This systematic analysis of CF parameters is one of only few such studies encompassing nearly whole series of RE(3+) ions.