Energy Levels and Optical Spectroscopy of Er3+ in Gd2O3 Nanocrystals

Based on the high-resolution excitation and emission spectra at 10 and 297 K, we have determined 107 crystal-field (CF) levels below 43 000 cm-1 of Er3+ at the C2 site of Gd2O3 nanocrystals. The levels were analyzed in terms of 16 free-ion and 14 CF parameters. The CF modeling of the experimental energy levels yielded physically reasonable Hamiltonian parameters with a final root-mean-square deviation of 12.5 cm-1. A modified Judd-Ofelt (JO) intensity analysis was proposed in evaluating the spectroscopic parameters such as JO parameters, radiative lifetime, and branching ratios for rare-earth ions doped in nanocrystals. Three JO parameters were obtained (¿2,4,6) 4.96, 2.23, and 0.49, in units of 10-20 cm2). The effect of J-mixing was taken into account in the energy-level-fitting and in the J-J ′ transition intensity calculation, which is observed to be responsible for the significant increase of the radiative transition rate of 4S3/2. Furthermore, the luminescence lifetimes of several excited multiplets of Er3+ were measured, and vibronic side bands and self-absorption were observed in the 10 K emission spectrum. I