Site symmetry determination and selective excitation spectroscopy of Eu3+:ThO2 crystal

The emission spectra, excitation spectra and fluorescence decay curves of E u3+:ThO2 are reported and analyzed. The Eu3+ :ThO2 crystal was grown by the flux technique. Using selective dye laser excitation at 12 K and selection rules, site symmetries of Eu3+ ions in ThO2 are determined as O-h and C-3v . Their crystal field levels and lifetimes were measured and tabulated. The dependence of energy transfer and energy level position on temperature are also discussed.