Physical Review B

Spectra and energy levels of Tm3+:Y3Al5O12

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Absorption spectra of Tm3+:Y3Al5O12 are reported between 1.9 and 0.26 m at 15 and 90 K, and between 0.80 and 0.35 m at 1.6 K. Laser-excited emission obtained at 80 K is also reported from the Tm3+ manifolds D21, G41, H43, and F43 to the ground-state manifold, H63. The emission from D21 also includes transitions to Stark levels in manifolds F43, F33, and F23. Analysis of the emission spectra confirms the experimental crystal-field splitting deduced from an analysis of the hot-band absorption data. Both emission and absorption spectra indicate that Tm3+ ions occupy several different sites although the majority of Tm3+ ions appear to substitute for Y3+ ions in dodecahedral lattice sites (D2 point-group symmetry). The most intense spectra are analyzed assuming selection rules for D2 symmetry. A lattice-sum calculation predicts a symmetry of 2 for the ground state. Using this result the symmetries of 20 1, 11 2, 17 3, and 18 4 Stark levels were identified experimentally and compared with results from a crystal-field splitting calculation. A Hamiltonian consisting of Coulombic, spin-orbit, interconfiguration-interaction, and crystal-field (D2 symmetry) terms was parametrized and diagonalized for all manifolds of the Tm3+(4f12) configuration. The rms deviation between 66 experimental and calculated Stark levels was 11 cm-1. © 1989 The American Physical Society.