Radiative Transition Probabilities in Tb³⁺ and Fluorescence Colors Producible by Tb³⁺-Activated Phosphors

For the purpose of evaluating the electric dipole and the magnetic dipole transition prababilities in Tb³⁺, the reduced matrix elements for ⁵D₄→⁷F_J and ⁵D₃→⁷F_J have been calculated. From the results, fluorescence colors producible by Tb³⁺-activated phosphors have been predicted: The best green colors with short persistence have the chromaticity coordinates around x=0.321, and y=0.651. For this purpose, Tb³⁺ ions should be embedded in lattice sites without inversion symmetry. The nonradiative transition probabilities for ⁵D₃→⁵D₄ due to multipolar interactions have been evaluated. When the Tb concentration is higher than several per cent, the quadrupole-dipole interaction between the Tb³⁺ ions in the metastable state ⁵D₃ and those in the ground state ⁷F₆ is predominantly responsible for the nonradiative ⁵D₃→⁵D₄ relaxation.