Abstract: GdTaO₄ and LuTaO₄ are heavy scintillators with fast decay fluorescence. The photoluminsecence spectra of M phase Nd∶GdTaO₄ and M′ phase Nd∶LuTaO₄ excited by a laser diode (LD) of 808 nm were fitted with the full-profile fitting method, and the transition intensity parameters A^k_t,p were determined. Under the excitation of 808 nm LD laser, the population ratio between the upper and low crystal field energy levels of ⁴F_3/2 for Nd³⁺ in GdTaO₄ is near to 1, but in LuTaO₄ is 1.30 and 1.41, which indicates that the relaxation rate between two crystal field energy levels is nearly equal to the excitation rate of LD. The Judd-Ofelt transition intensity parameters Ω_t were calculated with A^k_t,p, and the transition probabilities from ²P_3/2 of Nd³⁺ in GdTaO₄ and LuTaO₄ were computed, which indicates that the fast decay fluorescence of several hundred nanoseconds of Nd³⁺ in GdTaO₄ and LuTaO₄ is caused by the high nonradiative transition.

Key words: rare-earth tantalate, heavy scintillator, transition intensity, luminescence, nonradiative transition, population