YPO_4:Pr~(3+)发光的浓度和温度特性

选择激发YPO4:Pr3+ 中Pr3 + 离子的3P0 能级 ,测量了系列浓度样品不同温度下的发射光谱及 3P0 与1 D2 能级的发光衰减曲线。讨论了 6 13 2nm发射谱线的来源问题 ,确认是Pr3+ 离子的1 D2 (Γ3)→3 H4(Γ5 )的发射。研究了Pr3+ 离子3P0 与1 D2 能级不同的浓度猝灭关系 ,并用静态模型对1 D2 衰减曲线进行了拟合 ,结果显示1 D2 能级发光发生浓度猝灭的原因主要是相邻中心的偶极 四极相互作用引起的交叉弛豫。     

高转速下采用S-RESIDOR方法测量1H-27Al偶极偶合常数

提出利用S-RESIDOR(Symmetry-based Resonance Echo Saturation Irradiation DOuble Resonance)方法测量¹H-²⁷Al偶极偶合常数. 通过理论模拟,讨论了四极作用常数、饱和照射脉冲功率、照射时间对¹H/²7Al S-RESIDOR实验的影响. 发现四极作用常数对¹H/²⁷Al S-RESIDOR偶极去相曲线影响较小,中等强度的饱和照射功率即能满足实验要求. 高转速下,在氢型丝光沸石上进行了¹H/²⁷Al S-RESIDOR实验,测量得到Br-nsted酸位上的 ¹H与骨架上²⁷Al的偶极偶合常数为874 Hz.     

129Xe30+轰击Ni表面激发靶原子偶极跃迁和禁戒 (M1和E2)跃迁的特征光谱线

报道了用高电荷态离子129Xe30+(150keV) 轰击金属Ni表面，激发的200—1000nm NiⅠ和NiⅡ的特征光谱线的实验结果.实验结果表明：用电荷态足够高的离子作光谱 激发源，无需很强的束流强度（nA量级），便可有效地产生原子和离子的复杂组态间跃迁所 形成的可见光波段的特征谱线，特别是NiⅠ和NiⅡ偶极禁戒的电四极跃迁E2和磁偶极跃迁M1 的特征光谱线.通过分析发现，在禁戒跃迁的谱线中，有些是电子组态相同而原子态不同的 偶极禁戒跃迁光谱线而且NiⅡ的684.84nm谱线较强. 关键词： 光谱 禁戒跃迁 电子组态 高电荷态离子     

129Xe30+轰击Ni表面激发靶原子偶极跃迁和禁戒(M1和E2)跃迁的特征光谱线

报道了用高电荷态离子1 2 9Xe30 (15 0keV)轰击金属Ni表面 ,激发的 2 0 0— 10 0 0nmNiⅠ和NiⅡ的特征光谱线的实验结果 .实验结果表明 :用电荷态足够高的离子作光谱激发源 ,无需很强的束流强度 (nA量级 ) ,便可有效地产生原子和离子的复杂组态间跃迁所形成的可见光波段的特征谱线 ,特别是NiⅠ和NiⅡ偶极禁戒的电四极跃迁E2和磁偶极跃迁M1的特征光谱线 .通过分析发现 ,在禁戒跃迁的谱线中 ,有些是电子组态相同而原子态不同的偶极禁戒跃迁光谱线而且NiⅡ的 6 84 84nm谱线较强     

YPO4：Pr^3＋发光的浓度和温度特性

选择激发YPO4：Pr^3 中^Pr^3离子的^3Po级级,测量了系列浓度样品不同温度下的发射光谱及^3Po与^1D2能级的发光衰减曲线,讨论了613．2nm发射光谱线的来源问题,确认是Pr^3 离子的^1D2Г3）→^3H4(Г5）的发射。研究了Pr^3 离子^3P0与^D2能级不同的浓度猝灭关系,并用静态模型对^D2衰减曲线进行了拟合,结果显示^1D2能级发光发生浓度猝来的原因主要是相邻中心的偶极－四极相互作用引起的交叉弛豫。     

Y2O2S:Sm3+发光材料在不同激发波长的浓度特征

研究了在不同激发波长下三价钐离子掺杂硫氧化钇的发光强度对浓度的依赖关系。研究发现磷光体的发光强度不仅跟激活离子的浓度有关,而且跟激发时所采用的不同激发波长有关。磷光体发光强度与激活剂掺杂量的变化曲线表明,在不同激发路径下磷光体具有不同的发光性质。采用Sm^3 离子直接跃迁的413nm对样品进行激发时,发生猝灭的浓度低至约0．2mol％;当采用263nm高能紫外线激发时,浓度猝灭发生在较高浓度处(～2mol％),后者是前者的10倍。对Sm^3 离子发射强度与浓度关系曲线进行了拟合计算,结果表明Sm^3 在Y2O2S中浓度猝灭的原因主要是相邻中心的偶极-四极相互作用引起的交叉弛豫。     

类钴氙离子入射Ni表面激发的红外光谱线和X射线谱

当高电荷态类钴氙离子（cobalt like -Xe, Xe²⁷⁺）入射金属Ni表面过程中,共振电子俘获释放势能完成中性化,形成多激发态的Xe原子,其外壳层电子退激辐射红外光谱线.入射离子特殊的势能释放方式、离子动能和金属表面引起离子增益的能量在极短的时间（飞秒量级）沉积靶平方纳米尺度的空间范围,引起靶表面原子激发和电离,形成复杂组态之间的跃迁,特别是偶极禁戒跃迁（电四极跃迁、磁偶极跃）和X射线发射.单离子X射线产额随入射离子的动能增加而增加. 关键词： 高电荷态离子 红外光谱线 X射线 禁戒跃迁     

FeⅩⅪ离子电偶级、磁偶极及电四极跃迁振子强度的计算

讨论了使用MCHF方法优化径向波函数以获取大量原子参数的方法,由得到的波函数计算了FeXXI离子的相对论与非相对论能级,将计算能级与已有的实验结果进行了比较.对电偶极、磁偶极以及电四极的振子强度进行了非相对论与相对论修正的计算,对非相对论计算的振子强度,长度与速度两种表示符合较好.     

FeXXI离子电偶级、磁偶极及电四极跃迁振子强度的计算

讨论了使用MCHF方法优化径向波函数以获取大量原子参数的方法，由得到的波函数计算了FeXXI离子的相对论与非相对论能级，将计算能级与已有的实验结果进行了比较，对电偶极，磁偶极以及电四极的振子强度进行了非相对论与相对论修正的计算，对非相对论计算的振子强度，长度与速度两种表示符合较好。     

磁偶极和电四极在磁各向异性介质中的辐射功率

在经典电动力学的框架下,研究了磁各向异性介质中的电磁辐射问题,得到了磁偶极和电四极在磁各向异性介质中的辐射功率表达式.进一步地,通过把各向同性介质中的μrii代入所得辐射功率表达式,得到了与文献相符合的结果,验证了所得结果的正确性.研究结果表明磁偶极和电四极在磁各向异性介质中的辐射功率大小与磁各向异性介质的μrii大小有关,对判断磁偶极和电四极在磁各向异性介质中的辐射效果有较大的帮助.     

Adjustable, broadband, selective excitation with uniform phase

An advance in the problem of achieving broadband, selective, and uniform-phase excitation in NMR spectroscopy of liquids is outlined. Broadband means that, neglecting relaxation, any frequency bandwidth may be excited even when the available radiofrequency (RF) field strength is strictly limited. Selective means that sharp transition edges can be created between pure-phase excitation and no excitation at all. Uniform phase means that, neglecting spin-spin coupling, all resonance lines have nearly the same phase. Conventional uniform-phase excitation pulses (e.g., E-BURP), mostly based on amplitude modulation of the RF field, are not broadband: they have an achievable bandwidth that is strictly limited by the peak power available. Other compensated pulses based on adiabatic half-passage, like BIR-4, are not selective. By contrast, inversion pulses based on adiabatic fast passage can be broadband (and selective) in the sense above. The advance outlined is a way to reformulate these frequency modulated (FM) pulses for excitation, rather than just inversion.     

基于MTCA的HLS-Ⅱ直线加速器低电平系统改造

合肥光源(HLS-Ⅱ)在重大维修改造之后,其光源性能有了很大的提升。为了进一步实现连续、平稳地供光,需要对其进行恒流改造。恒流运行要求直线加速器的微波功率源有长期的稳定性与可靠性,旧的模拟低电平控制系统满足不了要求。本文基于微型电信计算平台(MTCA)设计实现了数字低电平控制系统,控制微波功率源的幅度和相位,它由以FPGA为核心的数字板卡、射频板卡、 MTCA机箱以及频率合成系统组成。该数字低电平系统工作在2 856 MHz的S波段,在线运行幅度稳定度达到0.04%,相位稳定度达到0.2°,满足恒流改造对直线加速器数字低电平系统0.25°相位抖动RMS值的相位精度要求。     

相位可控的核四极矩共振激励脉冲发生器设计

在核四极矩共振（NQR）领域,射频激励脉冲信号的优劣对NQR响应信号有重要影响.针对常规方法中射频激励脉冲参数不可控的问题,本文基于32位闪存微型控制器STM32和直接数字频率合成（DDS）芯片AD9910设计了一种相位可控激励脉冲发生器.采用STM32控制AD9910产生波形参数（脉冲宽度、脉冲间隔、脉冲个数和共振频率等）可控的射频激励脉冲,利用LabVIEW软件平台设计脉冲参数设置界面,并建立计算机与微控制器通信,实现波形参数的精确优化控制.实验结果表明,该方法实现了相位可控的NQR激励脉冲序列,可为后续NQR信号检测提供有效激励源.     

Octupolar excitation of ion motion in a penning trap

The excitation of the motion of ions in a Penning trap at twice their cyclotron frequency, 2ν _c , by means of an azimuthal octupolar RF field has been studied with the LEBIT facility at the NSCL. The possibility of such an RF octupolar excitation has been verified. Compared to ion excitation at ν _c by means of quadrupolar fields an increased resolving power is observed in the cyclotron resonance curves, which may have important implications for Penning trap mass measurements. Numerical simulations have been used to characterize important properties of this type of excitation in detail and to predict the behavior of the ion motion under realistic conditions. Good agreement with the experimental results is observed.      

磁共振现代射频脉冲理论在非均匀场成像中的应用

在磁共振非均匀场成像中，传统的射频脉冲导致回波信号的衰减.为了减小和消除这种磁共振信号的衰减，在讨论了经典理论的基础上根据非线性动力学中的逆散射理论和Shinnar-Le Roux方法导出了用于非均匀场成像的射频脉冲设计方法.模拟结果表明，采用逆散射理论和Shinnar-Le Roux方法优化的脉冲序列可以明显提高信号的信噪比. 关键词： 磁共振成像 射频脉冲 非线性系统     

Polarization-independent self-collimating bends and beam splitters in photonic crystals

Polarization independent bends and beam splitters for transverse electric (TE) and transverse magnetic (TM) polarizations have been demonstrated in two-dimensional (2D) photonic crystals (PhCs). In virtuel of equi-frequency contour analysis and finite-difference time-domain calculations, self-collimation behaviors for TE- and TM-polarizations are achieved at the same frequency. Simulation results show a 90-degree bend with 90% efficiency and beam splitters with about 96% total efficiency for both TE- and TMpolarizations, where the light is self-guided by the self-collimation effect. Such bends and beam splitters are expected to play important roles in optical devices where polarization insensitivity is needed.     

Single-shot measurement of quantum optical phase

Although the canonical phase of light, which is defined as the complement of photon number, has been described theoretically by a variety of distinct approaches, there have been no methods proposed for its measurement. Indeed doubts have been expressed about whether or not it is measurable. Here we show how it is possible, at least in principle, to perform a single-shot measurement of the canonical phase using beam splitters, mirrors, phase shifters, and photodetectors.     

A chemical-shift-insensitive slice-selective RF pulse (CHISS)

In NMR imaging and in vivo spectroscopy, slice selection is usually achieved by applying a frequency-selective RF pulse in the presence of a magnetic field gradient. A serious limitation of this method of slice selection is that, in a system with many different chemical shifts, the selected slice is offset in space for each chemically shifted resonance. In the present study, a composite RF pulse that is insensitive to chemical-shift differences has been developed. The pulse involves applying a RF pulse of desired shape in the presence of an alternating magnetic field gradient, together with hard 180° pulses at each gradient transition. Calculations are presented to show that excitation with the proposed pulse averages the chemical-shift term to zero. An exact calculation for a rectangular RF excitation shape verifies this. Experiments based on observing the RF excitation profiles have been performed to demonstrate the validity of the proposed pulse.     

88 W 0.5 mJ femtosecond laser pulses from two coherently combined fiber amplifiers

The generation of 0.5 mJ femtosecond laser pulses by coherent combining of two high power high energy fiber chirped-pulse amplifiers is reported. The system is running at a repetition frequency of 175 kHz producing 88 W of average power after the compressor unit. Polarizing beam splitters have been used to realize an amplifying Mach-Zehnder interferometer, which has been stabilized with a H?nsch-Couillaud measurement system. The stabilized system possesses a measured residual rms phase difference fluctuation between the two branches as low as λ/70 rad at the maximum power level. The experiment proves that coherent addition of femtosecond fiber lasers can be efficiently and reliably performed at high B-integral and considerable thermal load in the individual amplifiers.     

Fast electrons generation by RF and random fields near the antenna I. One dimensional model and regular fields

Test particle motion and acceleration has been explored in strong radio frequency (RF) fields, for which quasilinear ponderomotive force approximation is not valid. By nonlinear acceleration in spatially varying wave amplitude of RF travelling wave, electrons may be accelerated to time averaged velocities significantly larger than the RF wave phase velocity, and than the boundary plasma thermal velocity, in RF fields of several Volts per centimeter at wave frequency of 7 MHz. It is also demonstrated that even weak spatial gradients, much weaker than those expected in experiments, of the RF wave field amplitude, have significant consequences for the particle motion. Estimates are presented of the total energy transferred from the near antenna RF field to the plasma due to the nonlinear electron acceleration effects.