高密度闪烁体Nd∶GdTaO4和Nd∶LuTaO4发光跃迁强度计算

GdTaO₄和LuTaO₄是具有快发光衰减的新型重闪烁体。采用全谱拟合方法拟合了808 nm 激光二极管(LD)激发的M相Nd∶GdTaO₄和M′相Nd∶LuTaO₄的光致发光谱,给出了它们的跃迁强度参数A^k_t,p。在808 nm 激光激发下,GdTaO₄中Nd³⁺离子⁴F_3/2能级的上下两个晶场子能级的粒子布居数比例接近1,而在Nd∶LuTaO₄中则为1.30、1.41,表明在808 nm激光激发下,Nd³⁺的⁴F_3/2两个晶场子能级间的无辐射弛豫速率与激发速率相近。通过给出的跃迁强度参数A^k_t,p计算了Judd-Ofelt跃迁强度参数Ω_t,计算了Nd³⁺在GdTaO₄、LuTaO₄中的²P_3/2跃迁几率,表明GdTaO₄和LuTaO₄中Nd³⁺的数百纳秒发光跃迁是由高的无辐射跃迁几率导致的快发光衰减。

Optical Transition Intensity Calculation of High-Density Scintillator Nd∶GdTaO4 and Nd∶LuTaO4

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.