Sensitized luminescence of samarium in terbium fluoride

The results on the comparative study of photoluminescence (PL) spectra, PL excitation spectra, and PL relaxation of undoped and samarium-doped TbF3 crystals are presented. On the basis of these experimental results, the energy transfer peculiarities between Tb(3+ )and Sm3+ ions in the TbF3:Sm stoichiometric mixed crystal are studied. An efficient energy transfer from the Tb3+ ions to the Sm3+ ions is found. Based on the experimental results and the energy level diagrams for the Tb3+ and Sm3+ ions the mechanism behind such a process is explained. This made it possible to conclude that the emission bands (groups of lines) near 600 nm, at 640 - 650 nm and at 700 - 720 nm in the TbF3:Sm crystals are caused by the transitions from the (4)G(5/2) level to the H-6(7/2), H-6(9/2), H-6(11/2) levels, respectively. The 560 nm band is mainly caused by the transitions from the (4)G(7/2) level to the 6H9/2 level. The novelty of the obtained results lies in the proof that the shortest-wavelength emission band of Sm3+ ions in the samarium-doped TbF(3 )crystal is caused mainly by (4)G(7/2)-> H-6(9/2) transitions, not by (4)G(5/2)-> H-6(5/2) ones. This makes it necessary to investigate this luminescence band of Sm3+ ions in other matrices in more detail, first in matrices co-doped with terbium and samarium.