Luminescence properties of Pr3+ and Sm3+ ions in natural apatites

The luminescence spectra of Pr³⁺ and Sm³⁺ ions in apatite Ca₅[F∣(PO₄)₃] crystals from Spain and Russia have been compared with those for phosphate glasses doped with Pr³⁺, Sm³⁺ and Pr³⁺, Sm³⁺ ions. Time-resolved spectra measurements confirm that, in apatites, samarium ions occupy two non-equivalent crystal sites; the same is assumed for praseodymium ions. For the first time in minerals, the Stark splitting energy levels ΔE for ³H₆ and ¹D₂ of Pr³⁺ ion and ⁶H_7/2 of Sm³⁺ ion were determined. Some small differences in ΔE values for the Spanish and Russian apatite are discussed. The decay times of the excited levels of Pr³⁺, Sm³⁺ and Pr³⁺, Sm³⁺ doped in phosphate glass were measured at room temperature and at 77 K. The energy transfer process between samarium and praseodymium ions was observed and the energy transfer rate was calculated.