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 Tb3+ 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 4G5/2 level to the 6H7/2, 6H9/2, 6H11/2 levels, respectively. The 560 nm band is mainly caused by the transitions from the 4G7/2 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 TbF3 crystal is caused mainly by 4G7/2→6H9/2 transitions, not by 4G5/2→6H5/2 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.