ELECTRONIC ENERGY-LEVEL STRUCTURE, CORRELATION CRYSTAL-FIELD EFFECTS,AND F-F TRANSITION INTENSITIES OF ER3+ IN CS3LU2CL9

Single crystals of 1% Er3+-doped Cs3Lu2Cl9 were grown using the Bridgm an technique. From highly resolved polarized absorption spectra measur ed at 10 and 16 K, and upconversion luminescence and excitation spectr a measured at 4.2 K, 114 crystal-field levels from 27 L-2S+1(J)(4f(11) ) multiplets of Er3+ were assigned. 111 of these were used for a semie mpirical computational analysis. A Hamiltonian including only electros tatic, spin-orbit, and one-particle crystal-field interactions (C-3 up silon) yielded a root-mean-square standard deviation of 159.8 cm(-1) a nd could not adequately reproduce the experimental crystal-field energ ies. The additional inclusion of two-and three-body atomic interaction s, giving a Hamiltonian with 16 atomic and 6 crystal-field parameters, greatly reduced the rms standard deviation to 22.75 cm(-1). The furth er inclusion of the correlation crystal-field interaction (g) over cap (10A)(4), again lowered the rms standard deviation to a final value of 17.98 cm(-1) and provided substantial improvement in the calculated c rystal-field splittings of mainly the J =9/2 or J=11/2 multiplets. How ever, the calculated baricenter energies of some excited-state multipl ets deviate from their respective experimental values, and improvement s in the atomic part of the effective Hamiltonian are required to corr ect this deficiency of the model. On the basis of the calculated elect ronic wave functions, the 12 electric-dipole intensity parameters (C-3 upsilon) Of the total transition dipole strength were obtained from a fit to 95 experimental crystal-field transition intensities. The over all agreement between experimental and calculated intensities is fair. The discrepancies are most likely a result of using the approximate C -3 upsilon rather than the actual C-3 point symmetry of Er3+ in Cs3Lu2 Cl9 in the calculations.