Measurement of the beta+ and orbital electron-capture decay rates in fully ionized, hydrogenlike, and heliumlike 140Pr ions

We report on the first measurement of the beta+ and orbital electron-capture decay rates of 140Pr nuclei with the simplest electron configurations: bare nuclei, hydrogenlike, and heliumlike ions. The measured electron-capture decay constant of hydrogenlike 140Pr58+ ions is about 50% larger than that of heliumlike 140Pr57+ ions. Moreover, 140Pr ions with one bound electron decay faster than neutral 140Pr0+ atoms with 59 electrons. To explain this peculiar observation one has to take into account the conservation of the total angular momentum, since only particular spin orientations of the nucleus and of the captured electron can contribute to the allowed decay.     

镁铝类氢类氦类锂离子双电子复合速率研究

 镁铝类氢类氦类锂离子经中间双激发态进行的双电子复合过程在用双示踪元素谱线强度比研究ICF电子温度中占有很重要的地位。计算了双电子复合经不同Rydberg态跃迁通道的复合速率系数，并给出不同离化度的总的双电子复合速率系数的变化规律，比较了它们在不同电子温度和不同跃迁通道的异同，对研究X射线激光、等离子体温度诊断等诸多应用领域提供了有价值的原子数据。     

Simulating the resonance-mediated (1+2)-three-photon absorption enhancement in Pr3+ ions by a rectangle phase modulation

Enhancing the upconversion luminescence of rare earth ions is crucial for their applications in the laser sources, fiber optic communications, color displays, biolabeling, and biomedical sensors. In this paper, we theoretically study the resonance-mediated (1+2)-three-photon absorption in Pr³⁺ ions by a rectangle phase modulation. The results show that the resonance-mediated (1+2)-three-photon absorption can be effectively enhanced by properly designing the depth and width of the rectangle phase modulation, which can be attributed to the constructive interference between on-resonant and near-resonant three-photon excitation pathways. Further, the enhancement efficiency of resonance-mediated (1+2)-three-photon absorption can be affected by the pulse width (or spectral bandwidth) of femtosecond laser field, final state transition frequency, and absorption bandwidths. This research can provide a clear physical picture for understanding and controlling the multi-photon absorption in rare-earth ions, and also can provide theoretical guidance for improving the up-conversion luminescence.     

Temperature-dependent segregation of Pr3+ impurity ions in Y2SiO5:Pr3+ and YPO4:Pr3+ nanocrystals

Stationary and time-resolved spectroscopic methods are used to show that the impurity ions in Y₂SiO₅:Pr³⁺ and YPO₄:Pr³⁺ nanocrystals are distributed nonuniformly. This nonuniform distribution is found to be caused by the temperature-dependent segregation of Pr³⁺ ions near the surface of a nanocrystal. The motion of the activator ions from the bulk of a nanocrystal to the near-surface layer is traced when the activator concentration and the heat-treatment parameters are varied over wide ranges, and the main parameters of this effect (impurity redistribution intensity and time, diffusion coefficient) are estimated.     

类氢类氦类锂镁离子双电子复合的旁观电子角动量研究

类氢类氦类锂镁离子经中间双激发态进行的双电子复合过程在研究惯性约束聚变电子温度中占有很重要的地位.用准相对论方法计算了双电子复合经不同Rydberg态跃迁通道的复合速率系数,并给出不同离化度离子的双电子复合速率系数随电子温度的变化规律.显示出离子的相关能对峰值的电子温度有很大影响,当类氢离子跃迁通道的旁观电子角动量为1时双电子复合系数最大,而类锂离子是旁观电子角动量为3时最大. 关键词： 双电子复合 镁离子 角动量     

Optical transitions of Pr3+ and Er3+ ions in LiYF4

The optical absorption, emission, and excitation spectra of Pr³⁺ and Er³⁺ ions in LiYF₄ have been measured and energy level schemes established which agree with previous work. The temperature dependence of the emission lifetimes were investigated and analyzed using the Huang-Rhys and Struck-Fonger treatments of multiphonon decay. The non-radiative processes in LiYF₄: Er³⁺ were shown to follow the same “gap law” behavior as Er³⁺ in LaF₃ and MnF₂. Theoretical fits to the Huang-Rhys model allowed the construction of a configuration coordinate diagram for the Er³⁺ system. The non-exponential temperature dependence of the ¹D₂ lifetime in Pr³⁺ can be understood as a non-radiative transition from higher levels.     

类氢离子Mg^11＋,Al^12＋光谱参数的理论计算及在温度诊断中的应用

采用“多功能相对论原子结构计算程序“GRASP2（1992）,分别计算了类氢离子Mg^11 ,Al^12 能级之间电偶跃迁（E1）的波长,几率和振子强度,其中跃迁波长值与实验值相吻合,充分利用计算结果,采用等电子线率法对文献[4]的谱线强度比测温实验进行理论上的探讨,即利用原子序数相差不大（ΔZ=1,2)的两种示踪原子相同离化态的同种跃迁谱线进行电子温度诊断,以期望提高测温精度。     

Observation of one correlatedα-decay in the reaction58Fe on209Bi→267109

We report laser spectroscopic measurements of isotope shifts and hyperfine structure in ten stable and unstable lead isotopes, including two not previously measured.     

Anomalous reduction of the β-decay rate due to resonant energy absorption

This paper discusses the temperature dependence of the β-radioactivity rate associated with accompanying energy absorption process in condensed matter. The theoretical estimates are compared with recently reported experimental data.     

LED白光源用Pr3+,Ce3+:YAG光纤制备与特性

采用激光加热基座法制备LED白光源用Pr3+,Ce3+:YAG单晶光纤荧光材料,对所制备材料的荧光光学特性进行了实验分析结果表明,在Pr3+和Ce3+共掺发光过程中,Pr3+离子的发光可以通过Ce3+敏化作用使得其610 nm谱线荧光强度得到有效增强|利用所制备Pr3+,Ce3+:YAG单晶光纤荧光材料与蓝色LED合成产生高效LED光纤白光源,光源的色坐标为(x＝0.322,y＝0.335),显色指数84.3,表明光源品质良好,有望用于未来高效大功率光纤白光源.     

Anomalous reduction of the β-decay rate due to resonant energy absorption

The solvable model of a periodic array of quantum dots in a magnetic field is investigated. It is shown that in the case of square lattice and irrational flux the energy spectrum of a charged particle in the array has a fractal structure. In the case of honeycomb lattice the existence of an additional splitting of magnetic bands related with lattice geometry. The position of the Van Hove singularities is determined.     

Strong segregation of doped ions in Y2SiO5:Pr3+ nanocrystals

Strong temperature controlled segregation of doped ions in Y₂SiO₅:Pr³⁺ nanocrystals detected by spectroscopic techniques is reported. The elastic interactions stimulate Pr³⁺ segregation thus leading to non-uniform distribution of doped ions, pair formation and, as a consequence, to abnormal low threshold of luminescence concentration quenching for Y₂SiO₅:Pr³⁺ nanocrystals.     

Polarized spectral properties of Pr3+ ions in NaGd(MO4)2 crystal

A Pr³⁺:NaGd(MoO₄)₂ single crystal has been grown by the Czochralski method. The polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay curves of the crystal were measured at room temperature. The Judd–Ofelt intensity parameters Ω _t,q (t=2,4,6) and the spectroscopic parameters related to the ³ P ₀ and ¹ D ₂ multiplets were obtained and analyzed. The decay mechanisms for the ³ P ₀ and ¹ D ₂ multiplets were also discussed.     

Spectral properties of Pr3+ ions in Bi2(MoO4)3 crystal

A Bi₂(MoO₄)₃ single crystal doped with Pr³⁺ ions has been grown by the Czochralski technique. The polarized absorption and fluorescence spectra as well as the fluorescence decay curve of Pr³⁺ ions in the crystal were measured at room temperature. The spectroscopic parameters, including the Judd–Ofelt intensity parameters Ω_t (t=2, 4, and 6), spontaneous emission probabilities, fluorescence branching ratios, radiative lifetimes, stimulated emission cross sections, and fluorescence quantum efficiencies, were calculated. The spectral properties related to laser performance of this crystal were analyzed. The ¹ D ₂ multiplet of the crystal may be a good upper level for a solid-state laser.     

Qubits based on spectrally selected groups of Pr3+ ions in a LaF3 crystal

JETP Letters - Spectral selection, i.e., the separation of a group of particles with a spread in resonance frequencies smaller than the hyperfine splitting of working levels has been implemented by...