Spectroscopy of divalent rare earth ions in fluoride crystals

We have studied the absorption spectra of x-ray irradiation-induced Ce²⁺ and Pr²⁺ ions in crystals of alkaline-earth fluorides. We have calculated absorption spectra of divalent praseodymium ions in SrF₂ crystals doped with Pr²⁺ for the first time. The calculated spectra agree rather well with the experimental data. In crystals containing induced Ce²⁺ ions we have found strong electron–phonon coupling. In BaF₂, we do not observe bands corresponding to divalent Ce or Pr ions. - Highlights: • Pr²⁺ and Ce²⁺ ions were found in SrF₂ and CaF₂. • Ab initio calculation of Pr²⁺ ions was performed. • Good agreement between calculated and measured spectra. • Strong electron–phonon coupling with Ce²⁺ ions. • Strontium fluoride crystals would be useful as newly perspective scintillator.