Research On The Luminescent Properties Of High-lying Excited States Of Pr～(3+) And Nd～(3+)

High-lying excited states of Pr³⁺ are with unique luminescence properties. The highest state of 4f² configuration is ¹S₀. In certain hosts, ¹S₀ is located below the lowest state of 4f5d configuration, quantum cutting process may take place after vacuum UV excitation. In other hosts, ¹S₀ is above the bottom of the 4f5d configuration, and 4f5d-4f² emission may be observed. Thus Pr doped materials may be applied as the UVU excited phosphors, tunable laser of lasers and scintillators.In the thesis, we have prepared Pr and Nd doped materials and investigated their spectroscopic properties especially in the UVU region, and got the following conclusions:1. In SrAl₁₂O₁₉: Pr³⁺ both 4f^{2 1}S₀ and 4f5d emissions can be observed at high temperature under VUV excitation. Relative intensity of the broad band 4f5d emission increases with temperature increasing. The temperature dependence of the relative intensity may be well fitted with the model that the population of 4f5d is from thermal excitation of 4f^{2 1}S₀. This process further reduces the efficiency of visible emission in quantum cutting, and it must be considered in developing quantum cutting materials.2. In KLu₃F₁₀:Pr³⁺ and NH₄Lu₂F₇:Pr³⁺, Pr³⁺ ions may occupy two different types of sites. They are distinguished both by the emission and decay properties. One may be excited by 182 nm and with both 4f5d and 4F²(¹S₀) emissions, while the other may be excited by 209nm and with only 4f5d and 4f²(¹S₀) emission. With 193 nm laser pulse excitation, both sites can be excited. The decay curve can be fitted with a sum of two exponential decay functions.3. Host absorption and Nd³⁺ 4f³-4f²5d absorption bands can be observed in YAG: Nd³⁺ excitation spectrum monitoring at 398 nm, where both the self trapped exciton (STE) emission and Nd³⁺ emission exist. After host excitation, electrons and holes are either be trapped forming STE or transfer energy to Nd³⁺, resulting subsequently in STE emission and Nd³⁺ emission. With Nd concentration increases, concentration quenching takes place and Nd³⁺ 4f³-4f²5d absorption bands in the excitation spectrum decrease, while the STE emission related host excitation band keeps almost constant.