Time‐Resolved Synchrotron Radiation Excited Optical Luminescence: Light‐Emission Properties of Silicon‐Based Nanostructures

The recent advances in the study of light emission from matter induced by synchrotron radiation: X‐ray excited optical luminescence (XEOL) in the energy domain and time‐resolved X‐ray excited optical luminescence (TRXEOL) are described. The development of these element (absorption edge) selective, synchrotron X‐ray photons in, optical photons out techniques with time gating coincide with advances in third‐generation, insertion device based, synchrotron light sources. Electron bunches circulating in a storage ring emit very bright, widely energy tunable, short light pulses (<100 ps), which are used as the excitation source for investigation of light‐emitting materials. Luminescence from silicon nanostructures (porous silicon, silicon nanowires, and Si–CdSe heterostructures) is used to illustrate the applicability of these techniques and their great potential in future applications.     

硬X射线磁圆二色实验方法的建立

在北京同步辐射装置(BSRF)1W1B光束线和XAFS实验站上国内首次建立了硬X射线波段的磁圆二色实验(XMCD)方法. 以单晶金刚石作为相位延迟片, 在透射劳埃(Laue)模式下, 利用衍射双折射效应, 将入射的单色线偏振光转变为相应的左旋和右旋圆偏振光, 测量磁化样品对左旋和右旋圆偏振光吸收的差异, 获得了XMCD信号. 本实验使用透射方法测量了Pt-Fe合金Pt L_2,3边的XMCD, 获得了XMCD信号. XMCD实验方法的建立, 为研究磁性材料尤其是磁性薄膜材料的电子结构和磁结构提供了实验基础.     

Bromine Adsorption and Thermal Stability on Rh(111): A Combined XPS,LEED and DFT Study

This study addresses a fundamental question in surface science: the adsorption of halogens on metal surfaces. Using synchrotron radiation-based high-resolution X-ray photoelectron spectroscopy (XPS), temperature-programmed XPS, low-energy electron diffraction (LEED) and density functional theory (DFT) calculations, we investigated the adsorption and thermal stability of bromine on Rh(111) in detail. The adsorption of elemental bromine on Rh(111) at 170 K was followed in situ by XPS in the Br 3d region, revealing two individual, coverage-dependent species, which we assign to fcc hollow- and bridge-bound atomic bromine. In addition, we find a significant shift in binding energy upon increasing coverage due to adsorbate-adsorbate interactions. Subsequent heating shows a high thermal stability of bromine on Rh(111) up to above 1000 K, indicating strong covalent bonding. To complement the XPS data, LEED was used to study the long-range order of bromine on Rh(111): we observe a (√3×√3)R30° structure for low coverages (≤0.33 ML) and a star-shaped compression structure for higher coverages (0.33–0.43 ML). Combining LEED and DFT calculations, we were able to visualize bromine adsorption on Rh(111) in real space for varying coverages.     

燃烧：一个不息的话题——同步辐射单光子电离技术在燃烧研究中的应用

燃烧应用于工业、农业、交通运输、国防等各个领域,提供了当今社会极大部分的能量需求.100多万年前人类就开始利用燃烧,人类研究燃烧已经有150多年的历史.本文介绍了将同步辐射真空紫外单光子电离技术结合分子束取样,应用于燃烧研究中,可以探测到燃烧中的各种中间物,包括稳定的和不稳定的产物.通过扫描光子能量,测量产物的光电离效率谱,可以区分其同分异构体.因此,利用这种新的诊断技术,在150年后的今天,我们仍然可以在火焰中发现很多新的燃烧中间体,为发展燃烧动力学模型提供精确的实验数据.最后,展望该方法在其它学科中的可能应用.     

Spatial and spectral characteristics of laser-field synchrotron radiation

The spatial and spectral characteristics of laser-field synchrotron radiation (LSR) are investigated. The results show that LSR is emitted normal to the laser axis and emission in the X-ray wavelength can be obtained by increasing the intensity of the laser pulse and the initial energy of the electron. The unique feature offered by the laser-field synchrotron radiation (LSR) makes them a promising compact source of light at shorter wavelengths.     

分子的飞秒强光电离

文章以一个实验者的角度,介绍了分子的飞秒强光电离的研究现状.文章从对比飞秒激光电离质谱与纳秒激光电离质谱开始,接着介绍分子在激光场作用下的可能电离机理,着重描述了几个处理分子场致电离的理论模型和实验验证,最后对飞秒激光导致的分子在激光脉冲作用后取向研究进行了简单介绍.     

KTP(001)晶体分光性能研究

根据同步辐射光源对软X射线分光晶体的性能要求,分析了软X射线能区常用分光晶体的性能优劣,指出对于晶格常数值大的分光晶体,KTP(KTiOPO₄)(011)是该能区比较理想的分光晶体. 同时提出了一种利用同步辐射光源测量晶体衍射效率的实验方法,指出光源的发散度与晶体的衍射效率密切相关. 测量了KTP(011)晶体的晶格常数,给出了KTP(011)晶体的实测衍射效率. 关键词： 同步辐射 KTP(011)晶体 衍射效率 光源发散度     

Penetrating view of nano-structures in Aleochara verna spermatheca and flagellum by hard X-ray microscopy

A penetrating view of the three-dimensional nanostructure of female spermatheca and male flagellum in the species Aleochara verna is obtained with 100-nm resolution using a hard X-ray microscope, which provides a fast noninvasive imaging technology for insect morphology. Through introducing Zernike phase contrast and heavy metal staining, images taken at 8 keV displayed sufficient contrast for observing nanoscale fine structures, such as the spermatheca cochleate duct and the subapex of the flagellum, which have some implications for the study of the sperm transfer process and genital evolution in insects. This work shows that both the spatial resolution and the contrast characteristic of hard X-ray microscopy are quite promising for insect morphology studies and, particularly, provide an attractive alternative to the destructive techniques used for investigating internal soft tissues.     

Characterization of trace embedded impurities in thin multilayer structures using synchrotron X‐ray standing waves

X‐ray standing wave (XSW) field generated under Bragg reflection condition in a periodic Mo/Si multilayer structure has been used to determine the concentration and location of various trace element contaminants embedded in different layers of that multilayer structure. We have used intense synchrotron X rays for XSW analysis. It is observed that various trace element impurities such as Cr, Fe, Ni and W get embedded unintentionally in the multilayer structure during the deposition process. Consequences of such impurity incorporation on the optical properties of the multilayer structure are discussed in hard and soft X‐ray regions. Present measurements are important in order to optimize the deposition methods on one hand and to better correlate the measured optical properties of a multilayer structure with theoretical models on the other. Copyright © 2010 John Wiley & Sons, Ltd.     

中国散裂中子源快循环同步加速器壁电流探测系统

在中国散裂中子源工程中, 快循环同步加速器负责将剥离注入的能量为80MeV的质子束加速至1.6GeV后引出。在快循环同步加速器上共安装了两台壁电流探测器, 用来观测束流从注入至引出过程中束团在时域上的变化情况。详细介绍了壁电流探测器在陶瓷间隙、磁性材料和匹配电阻等方面的设计考虑, 以达到带宽满足百kHz到30 MHz的设计目标, 并对实际带束流测量结果进行分析讨论。经实际在线运行测试, 此壁电流探测器完全满足束流调试及运行需要。