ENERGY-LEVEL AND LINE-STRENGTH ANALYSIS OF OPTICAL-TRANSITIONS BETWEEN STARK LEVELS IN ND3+Y3AL5O12

Results obtained from optical absorption measurements on Nd3+:Y3Al5O12 (Nd:YAG) at 10 and 29 K are reported and analyzed. The low-temperature (10 K) absorption spectrum shows transitions from the lowest Stark component of the 4I9/2 (ground) multiplet to 133 of the 155 crystal-field (Stark) levels predicted to be located between 3900 and 40 000 cm-1, spanning 35 excited multiplet manifolds of Nd3+(4f3). Among the 133 transitions observed in the 10-K absorption spectrum, 97 are sufficiently well resolved to permit quantitative determination of transition line strengths. Energy levels for the 4I9/2 and 4I11/2 multiplets are taken from previously obtained optical emission measurements, and the resulting 144-level data set is analyzed in terms of a model Hamiltonian that assumes D2 site symmetry for the Nd3+ ions in Nd:YAG. Inclusion of two-electron correlation crystal-field (CCF) interaction terms in the model Hamiltonian explains the crystal-field splittings of several anomalous multiplets, and reduces the rms deviation between calculated and observed energies (for 144 levels) from 28 to 14 cm-1. The optical line-strength data obtained in this study are analyzed in terms of an f-f transition intensity model developed by us in previous work. This model has broad applicability in analyses of f-f intensity data for transitions between Stark levels. Emission branching ratios for transitions from the 4F3/2 multiplet are calculated and compared with literature values. © 1994 The American Physical Society.