Energy levels, fluorescence lifetime and Judd–Ofelt parameters of Eu³⁺in Gd₂O₃nanocrystals

Crystal-field (CF) levels below 36 000 cm −1 of Eu 3+ at the C 2 site of Gd 2 O 3 nanorods are experimentally determined from the excitation and emission spectra at 10 K. The levels are analysed in terms of 20 freely varied free-ion and CF parameters, and energy-level fit yields a final standard deviation of 12.9 cm −1 , showing very good agreement between the observed and the calculated values. The Judd–Ofelt (JO) intensity parameters Ω 2,4,6 are determined to be 12.39, 2.02 and 0.19 (in 10 −20 cm 2 ) which takes J-mixing into account. For the first time the absolute value of the Ω 6 parameter is reliably determined. The calculated radiative transition rates and branching ratios for the transitions from 5 D 0 agree well with the experiments. The size dependence of the JO intensity parameters of Eu 3+ in RE 2 O 3 (RE = Y, Gd, Lu) nanocrystals is clarified. The fluorescence lifetime of 5 D 0 of Eu 3+ in Gd 2 O 3 nanorods is observed to be significantly affected by the surrounding media, giving rise to a filling factor of 0.58 for the nanoparticles.