Field of Expertise: Advanced Material Science

Hypersensitive transitions of Eu3+: experimental and theoretical study
A. Wernbacher, C. Holzer, A.-M. Kelterer, K. Gatterer
Institute of Physical and Theoretical Chemistry
15:20 - 17:30 Thursday 24 October 2013 Foyer Alte Technik

The rare earth ion Eu3+ is widely used in phosphor technology as a red luminophore, e.g. in colour television screens or on euro banknotes [1]. An interesting feature of rare earth ion spectra are hypersensitive transitions, which exhibit a significant intensity change if the environment surrounding the rare earth ion is varied, while the intensities of the other transitions remain nearly unchanged. Eu3+ shows two hypersensitive transitions, namely the 7F0 → 5D2 transition in absorption and the 5D0 → 7F2 transition in emission.
In this study the absorbance and emission spectra of Eu3+ were investigated with experimental and theoretical methods including Judd-Ofelt theory and relativistic ab initio calculations. The aim of this ongoing study is to determine the symmetry dependence of the intensity change of the hypersensitive transitions. Therefore, the optical spectra of Eu3+ in mixtures of 0 – 100 % acetone in water were measured and the Judd-Ofelt intensity parameters Ωλ (λ = 2, 4) evaluated. Furthermore, several structures of Eu3+ with 6 – 9 water molecules in different symmetries (e.g. Th, D3h) were optimized (DFT, large effective core potential).
The excitation energies of the experiment are compared with the values obtained with computational methods. The 4f-4f transition energies of the free ion were computed using the relativistic correlation modules of the DIRAC12 [2] program package with a 4-component Dirac-Coulomb Hamiltonian including spin-spin and spin-same orbit interactions and different correlation spaces.
[1] Cotton, S.; Lanthanide and actinide chemistry; Wiley: Chichester, England Hoboken, NJ, 2006.
[2] http://www.diracprogram.org