Cathodoluminescence and laser-excited luminescence spectroscopy of Eu3+ and Eu2+ in synthetic CaF2: A comparative study

A comparative study of laser-excited luminescence and cathodoluminescence of CaF2:0.1% EuF3 at room temperature was performed to determine the position and relative intensity of EU(3+)and EU(2+) main emission lines in CaF2. Cathodoluminescence spectra show a major peak at 424 nm which is related to the electric dipole allowed 4f(6)5d-4f(7) transition of the Eu2+ ion. The cathodoluminescence peaks of the EU(3+) ion are very weak and are not easily identifiable. Photoluminescence spectra recorded under different laser excitation conditions (corresponding to the F-7(0) --> D-5(0) transition of the EU(3+) ion) reveal major peaks around 590 nm due to the magnetic dipole allowed F-7(0) --> D-5(1) transition of the EU(3+) ion in three different environments: tetragonal, dimer and cubic. We emphasize the necessity of using a tunable laser to unambiguously identify the EU(3+) ions in the minerals.