在空气-乙炔焰中络合剂对镱的增感效应

本文在空气-乙炔焰中,借加入有机络合剂以提高能形成难离解氧化物的稀土的灵敏度。以镱为例,研究了含键合原子氧或氧、氮的络合剂对镱的增感效应和镱原子在火焰中的分布。Yb灵敏度达0.17μg/ml/1%吸收,选择性显著提高。本法用于合成样品中镱的测定,结果满意。     

冷镱原子精密光谱的研究进展

文章简要介绍了冷原子精密光谱研究方面的重要进展,报道了作者所在课题组近年来在镱原子的激光冷却与囚禁、光晶格中冷镱原子的量子操控、冷镱原子钟跃迁谱的精密测量、冷镱原子光钟的闭环锁定和频率稳定性测量等方面所取得的最新研究结果,最后对光学原子钟的发展进行了展望。     

四通道超稳腔的振动分析及热分析

镱原子光钟是当前稳定度最好的光钟,其稳定度已经进入10?19的量级.依托于高精度的镱原子光钟,可以开展广义相对论的检验以及测地学等领域的科学和应用研究.镱原子光钟研制过程中需要用到多种频率的光,所以针对这些激光的频率控制是镱原子光钟研制的一项关键技术问题.本文针对钟激光以外其他四种激光的频率控制要求,以一个四通道超稳光...     

宇称破缺实验的新突破

美国物理学家在实验中观测到最显著的宇称破缺现象,他们用镱原子取代铯原子,实验数据显示镱原子实验比铯原子实验要显著一百倍.在进一步的工作中,这个实验的数据可以揭示中子在原子核内的分布,进而使科学家有机会了解弱相互作用在原子核内部的作用过程和效果.     

用于镱原子光钟759nm光晶格激光的频率锁定

本文报道了一种用于镱原子光钟的759nm光晶格激光频率锁定方法。759nm激光通过PoundDrever-Hall(PDH)技术锁定在一个腔长为10cm的超低膨胀系数(ULE)的高细度Fabry-Perot(FP)腔上。激光频率被锁定后的测量结果表明,759nm的光晶格激光线宽被压窄到小于200kHz;运用频率锁定的759nm激光和飞秒光梳拍频来监测超稳腔的长期漂移率,结果显示ULE超稳腔的漂移率为0.16 Hz/s。将锁定后的759nm光晶格激光用于镱原子光钟光晶格的装载,实现了镱原子在光晶格场中的稳定装载以及对光晶格场频率的精确控制,从而为镱原子光钟的闭环运转做了必要的技术准备。     

镱、钠共掺的氟化钙晶体在1050nm的可饱和吸收作用

通过在稳定连续波运转的Yb:YAG 激光器中插入不同掺杂浓度的新型钠、镱共掺的氟化钙晶体的对比性实验,证明了镱、钠共掺的氟化钙晶体在1050nm具有明显的可饱和吸收作用,从而解释了该晶体作为增益介质在该波段总是趋于自调Q运转的原因.Yb³⁺离子是该晶体可饱和吸收作用的主要因素,但是共掺入适当的Na离子可以明显改善晶体的调Q效果.优化共掺镱、钠离子的浓度和比例后的氟化钙晶体能够作为1050nm波段激光器的被动Q开关. 关键词： 镱、钠共掺氟化钙 可饱和吸收体 调Q     

镱原子光钟基于FPGA控制系统的数据处理

高精度光钟被认为是广义相对论验证,相对论测地学以及暗物质探测的重要工具。镱原子光钟是目前国际上稳定度最好的光钟,通过36 h的平均可以进入10~(-19)的量级。控制系统是镱原子光钟的重要组成部分,它主要负责光钟系统的时序控制。本文提出一种基于Python语言支持的现场可编程门阵列(FPGA)控制系统,通过编译和调用Python程序包在FPGA上运行,用来产生光钟运行过程所需的各种控制信号,以及对镱原子光钟工作过程中获取的数据进行存储和后期处理。研究结果表明:基于FPGA控制系统的数据处理可以完全匹配传统Matlab和Origin软件的数据处理方法,获取μK量级冷原子的温度和Hz量级的钟跃迁谱线宽;另外,对复杂钟跃迁谱线实现高斯基函数的多峰拟合,通过与早期实验过程中噪声分析建立的数据库进行比对,用来作为光钟运行的过程分析和故障诊断,有助于未来将机器学习引入高精度原子光钟的数据处理用来实现引力波以及暗物质的探测。     

中子辐照对掺镱光纤材料光学特性的影响

采用改进型化学气相沉积法结合稀土螯合物掺杂制备了系列掺镱光纤预制棒及光纤,并测试了光纤(预制棒)辐照、退火前后的光学性能.结果表明:中子辐照后掺镱光纤材料中与Al相关的缺陷浓度增多,导致光纤材料在可见光区域吸收损耗增加.Ce离子的掺杂可缓减铝氧空位中心(Al-OHC)等色心缺陷的增加,从而有效抑制掺镱光纤的辐致暗化效应.热退火可降低中子辐致色心缺陷的浓度从而降低光纤材料的吸收,在一定程度上消除暗化效应.     

基于粉末烧结技术制备镱铝共掺大模场光子晶体光纤

采用粉末烧结技术制备出高浓度镱铝共掺石英棒,Yb3+掺杂浓度为12 000 ppm(wt).利用此掺镱石英棒作为纤芯,拉制出镱铝共掺大模场光子晶体光纤,光纤模场面积为550μm2,模场直径26 μm.实验结果表明:光纤在近红外波段(850～1 033 nm)出现一个宽的吸收带,主吸收峰波长位于976 nm,在此波长处吸收损耗高于10 dB/m;采用波长为971 nm的激光泵浦光纤,在1 050～1 125 nm波长范围内产生高斯型的荧光峰,峰值波长位于1 088 nm处,荧光半宽高45 am.     

基于粉末烧结技术制备镱铝共掺大模场光子晶体光纤

采用粉末烧结技术制备出高浓度镱铝共掺石英棒,Yb3+掺杂浓度为12 000ppm(wt).利用此掺镱石英棒作为纤芯,拉制出镱铝共掺大模场光子晶体光纤,光纤模场面积为550μm2,模场直径26μm.实验结果表明:光纤在近红外波段(850～1 033nm)出现一个宽的吸收带,主吸收峰波长位于976nm,在此波长处吸收损耗高于10dB/m;采用波长为971nm的激光泵浦光纤,在1 050～1 125nm波长范围内产生高斯型的荧光峰,峰值波长位于1 088nm处,荧光半宽高45nm.     

Time domain finite volume method for the transient response and natural characteristics of structural-acoustic coupling in an enclosed cavity

A time domain finite volume method（TDFVM）based on wave theory is developed to analyze the transient response and natural characteristics of structural-acoustic coupling problems in an enclosed cavity.In the present method,the elastic dynamic equations and acoustic equation in heterogeneous medium are solved in solid domains and fluid domains respectively.The structural-acoustic coupling is implemented according to the continuity condition of the particle velocity along the normal direction and the normal traction equilibrium condition on the interface.Several numerical examples are presented to validate the effectiveness and accuracy of the present TDFVM.Then the effects of water depth on the acoustic and vibration characteristics and the natural characteristics of a structural-acoustic coupling system are analyzed.The numerical results show that the increase of water depth leads to a stronger coupling between the water and structure and the decrease of natural frequencies of coupling system,The computational cost and memory of this method are small and it can be applicable to structural-acoustic coupling problems in the heterogeneous fluid.     

Modeling Gain Dynamics in EDFAs: Space-Resolved Versus Lumped Models

We present a detailed comparison of dynamic space- and frequency-resolved and lumped erbium-doped fiber amplifier (EDFA) models. The space- and frequency-resolved models are based on an iterative solution of propagation equations for pump, multiple signals, and spectral components of forward and backward propagating amplified spontaneous powers and rate equations for pump, metastable, and ground energy level population densities of erbium ion. In contrast to space-resolved models, the lumped model solves a single ordinary differential equation for time evolution of the length-averaged metastable level population and is therefore substantially less computer time consuming. Both the space, and frequency-resolved and the lumped models give almost identical results when used for an analysis of surviving channel power excursions in concatenated EDFAs fed by multiwavelength signal and add/drop scenarios. For a statistical analysis of output power and signal-tonoise ratio fluctuations in EDFA cascades fed by burst-mode packet traffic, only lumped models can be used.     

镧和铕与邻菲罗啉谷氨酸配合物的NMR和IR研究

合成了稀土镧和铕与谷氨酸，邻菲罗啉形成的二元及三元配合物，经元素分析确定该配合物的组成为Ｌｎ（ｐｈｅｎ）（Ｇｌｕ）３．７Ｈ２Ｏ（Ｌｎ＝Ｌａ，Ｅｕ）；Ｅｕ（Ｇｌｕ）３；１２Ｈ２Ｏ。用核磁共振和红外光谱研究与配体与稀土离子的配位方式，讨论了稀土离子的顺磁性及屏蔽效应对配合物的ＮＭＲ谱图的影响。     

利用ICP-AES分析大豆体内Mn和Zn分配及收支平衡

长期定位试验和ICP-AES测试相结合,研究了下辽河平原土壤有效Mn和Zn浓度变化以及不同施肥制度下大豆体内Mn和Zn浓度与含量的变化。结果表明：下辽河平原土壤有效Zn浓度已濒临临界值,应加强对其监测;大豆籽实和秸秆体内Zn浓度受施肥影响变化较小;而籽实中Mn浓度受施肥影响变化较大,且NPK和NPKO处理显著高于O和CK处理;养分循环再利用在增加大豆生物量的同时,Mn和Zn携出亦呈增加趋势;土壤-作物系统中,Mn和Zn均出现收支赤字,其赤字大小顺序为NPKO＜O＜CK＜NPK,表明养分循环可以显著减缓这种赤字,使生态系统更可持续。     

Comparison between formulas of rotational band for axially symmetric deformed nuclei

The experimental rotational spectra of the deformed nuclei available in even-even and odd-A nuclei in the rare-earth and actinide regions are systematically analyzed with several rotational spectra formulas,including Bohr-Mottelson's I(I+l)-expansion,Harris'w2-expansion,ab and abc formulas.It is shown that the simple 2-parameter ab formula is much better than the widely used 2-parameter Bohr-Mottelson's AB formula and Harris'αβ formula.The available data of the rotational spectra of both ground-state band in even-even nuclei and one-quaasiparticle band in odd-A nuclei can be conveniently and rather accurately reproduced by ab formula and abc formula.The moment of inertia and the variation with rotational frequency of angular momentum can be satisfactorily reproduced by ab and abc formulas.     

Temperature Sensitivity Control and Mechanical Stress Effect of Boron-Doped Long-Period Fiber Gratings

We will present in this work the quantitative analysis of the relationship between the doping concentrations of GeO 2 and B 2 O 3 in the core and cladding regions and the temperature sensitivity of the resonance wavelength shift in long-period fiber gratings (LPFGs). Based on this analysis, the temperature sensitivity was suppressed and enhanced to 0.002 nm/°C and 0.28 nm/°C, respectively. We will also discuss the effect of the residual mechanical stress on the optical and mechanical properties of LPFGs. In particular, we will present the measurement results of the dependence of the refractive index change and mechanical strength on the residual mechanical stress in the boron-doped fibers with depressed clad and matched clad.     

Astrophysical combustion

There are three main astrophysical combustion systems: the evolution of stars, formation of interstellar dust and particulates, and the transition to hadrons in the early universe. These are described in terms of general combustion concepts, such as ignition, laminar and turbulent flames, detonations, multiphase flows, and particle and soot formation. Viewed in this way, the universe and many of its most important astronomical components are combustion systems, and we should use these as naturally occurring laboratories for exploring new and familiar combustion regimes. A more detailed discussion focuses on one type of combustion system, the ignition and development of turbulent flames in Type Ia supernovae, and the importance of the transition to a detonation.     

Design and simulation of the wire scanner for the injector linac of BEPC Ⅱ

BEPC Ⅱ,the upgrade project of Beijing Electron Positron Collider (BEPC),is an accelerator with large beam current and high luminosity,so an efficient and stable injector is required.Several beam diagnostic and monitoring instruments are used.A new diagnostic instrument--wire scanner,has been designed and will be used to nleasure the profile of the linac beam of BEPC Ⅱ.This paper describes the prototype of this system and the cause of heat generating of the wire.Some simulation results of the heat and force by using finite element method software-ANSYS(R),2) are presented and discussed.     

Synthesis of Pd and Rh metal nanoparticles in the interlayer space of organically modified montmorillonite

This study reports the synthesis of palladium and rhodium metal nanoparticles supported on montmorillonite (MMT) and partially organically modified MMT (POMM) using tetraamine palladium and hexaamine rhodium complex as precursor for palladium and rhodium respectively. The synthesized nanoparticles were characterized by powder X-ray diffraction PXRD and TEM. The PXRD study shows characteristic crystallographic planes for Pd and Rh metal and confirm the formation of metal nanoparticles in MMT and POMM. The TEM images reveal the effect of organic modification of MMT on decreasing particle size of Pd and Rh metal. The Pd and Rh metal nanoparticles are agglomerated in pristine MMT while nanoparticles are well dispersed in POMM. ICP-AES analysis was carried out to estimate quantitative amount of Pd and Rh metal in MMT and POMM.     

桂皮和小茴香中砷、铅、镉和汞的测定

用电感耦合等离子体-原子发射光谱法(ICP-AES)对桂皮和小茴香中的有害元素砷、铅、镉和汞进行了定量测定.结果表明,该方法简便可靠,具有良好的精密度和准确度.本文为桂皮、小茴香的种植及入药等方面提供了一些有用的信息.