北京同步辐射光电子能谱实验站近期实验概况

随着北京同步辐射光电子能谱实验站持续稳定的开放运行,用户基于该实验站提供的光电子能谱各种实验模式开展了从金属表面界面电子结构到纳米材料、掺杂金属富勒烯以及磁电阻氧化物体系电子结构的研究工作。本文中选择部分具有代表性的实验进行介绍。     

北京同步辐射光电子能谱实验站近期研究概况

随着北京同步辐射光电子能谱实验站持续稳定的开放运行，用户基于该实验站提供的光电子能谱各种实验模式开展了从金属表面界面电子结构到纳米材料、掺杂金属富勒烯以及磁电阻氧化物体系电子结构的研究工作。本中选择部分具有代表性的实验结果进行介绍。     

碳化硅表面锌的吸附及其热氧化的同步辐射光电子能谱研究

利用同步辐射光电子能谱(Synchrotron radiation photoelectron spectroscopy,SRPES)和X射线光电子能谱(X-rayphotoelectron spectroscopy,XPS)技术,研究了金属Zn在6H-SiC表面的吸附和热氧化以及ZnO/SiC的界面形成过程.研究结果表明,在SiC表面沉积金属Zn的初始阶段,Zn可以夺取SiC衬底表面残留的氧并与之成键.随着Zn覆盖度的增加,表面具有金属特性.在2.0×10-4Pa的氧气氛中180℃温度退火下,覆盖的Zn会被部分氧化形成ZnO,还有部分Zn因其在真空中的低蒸发温度而逸出表面.在同样的氧气氛中600℃温度退火后,覆盖的金属Zn全部被氧化而生成ZnO.在氧气氛中退火时,衬底也会轻度氧化,从而导致在ZnO/SiC界面处存在一层很薄的Si的氧化层.根据得到的光电子能谱的实验结果,计算出ZnO/SiC异质结的价带偏移为1.1 eV.     

Mn/6H-SiC(0001)界面的同步辐射光电子能谱研究

本文利用同步辐射光电子能谱（SRPES）和X射线光电子能谱（XPS）对金属Mn在6H—SiC（0001）表面的生长模式和Mn／6H-SiC（0001）界面进行了研究。实验结果表明,常温下金属Mn在6H—SiC（0001）表面上表现为二维层状生长模式。随着金属Mn沉积膜厚的增加,样品表面金属性明显增强。沉积过程中,金属Mn并未与SiC衬底发生反应,界面间由于能带弯曲导致费米能级向下移动,并计算出肖特基势垒高度（SBH）大约为1．79eV。当沉积膜厚达到2nm后,样品于250℃退火导致金属Mn向衬底扩散,但未与衬底发生反应。样品于500℃退火后界面间形成Mn的硅化物。     

同步辐射近常压光电子能谱及其应用

介绍了同步辐射近常压光电子能谱的基本概念、发展历程以及该技术的装置和原理。列举了几个近常压光电子能谱的应用领域。该技术填补了超高真空和真实条件下压强上的空白,在原位研究表面化学变化、催化反应,腐蚀以及电化学过程上有着很大的优势。     

类金刚石薄膜的同步辐射光电子能谱研究

利用同步辐射光电子能谱全电子产额模式(TEY)对石墨、金刚石薄膜和类金刚石薄膜(DLC)的ClsX射线吸收谱进行了研究。在高真空里表面净化处理后,在类金刚石薄膜的Cls吸收谱中分别观察到对应于金刚石sp^3杂化结构成分和石墨sp^2杂化结构成分的特征峰,说明了类金刚石薄膜是由碳sp^2、sp^3两种杂化结构无序混合形成的非晶碳结构;然后,测量了一系列类金刚石薄膜样品的ClsX射线光电子能谱(XPS),得到了每组样品的sp^2、sp^3成分比。     

聚乙烯醇修饰Fe3O4纳米颗粒的制备表征及同步辐射X射线光电子能谱研究

采用水溶性高分子聚合物聚乙烯醇(PVA)对Fe3O4纳米颗粒表面进行功能化修饰,利用透射电镜(TEM)、紫外可见吸收光谱(UV-vis)、Zeta电位检测、电感耦合等离子体质谱(ICP-MS)和热重分析(TGA),对包被前后Fe3O4的粒径、分散稳定性、PVA的包覆效率及纳米颗粒进入细胞的量进行了表征研究.通过同步辐射...     

葡聚糖修饰Fe3O4磁性纳米粒子的同步辐射光电子能谱研究

在纳米Fe3O4表面修饰葡聚糖可在粒子表面建立空间位阻稳定层,不仅提高了纳米粒子在水中的分散稳定性,还增强了纳米粒子的生物相容性.本文在柠檬酸钠介质中合成了葡聚糖修饰的Fe3O4纳米粒子,采用同步辐射X射线光电子能谱(XPS)对未经修饰和葡聚糖修饰后的Fe3O4纳米粒子表面的化学组分、表面原子的化学结构、化学键合情况进行了定性和定量分析,并给出葡聚糖修饰Fe3O4纳米粒子的反应机理.结果表明,反应体系中的柠檬酸钠首先在Fe-O-C键包覆到Fe3O4纳米粒子表面,然后葡聚糖分子与纳米粒子外的COO-以氢键结合并同时发生葡聚糖大分子缠绕包裹连接到纳米粒子表面,这大大增强了反应体系的分散稳定性和葡聚糖修饰氧化铁纳米粒子的亲水性.     

北京正负电子对撞机同步辐射X射线能谱的测量

本文提供了北京正负电子对撞机同步辐射光束线上X射线能谱的首次测量结果,文章对探测器和谱仪系统、测量方法及数据分析予以扼要的描述。     

同步辐射红外光谱研究结肠癌细胞的软X射线辐射效应

为探索红外光谱技术在辐射效应研究中的应用,以合肥同步辐射红外和远红外光谱实验站为平台开展软X射线低剂量辐射效应研究。用傅里叶变换红外显微镜光谱仪采集软X射线辐照前后的结肠癌细胞（HCT116）的单细胞光谱,分析光谱的位置和强度等变化。发现辐照后癌细胞吸收谱在峰的强度、位置都有明显变化,尤其位于1079 cm^-1、1236 cm^-1的核酸骨架磷脂对称和反对称振动吸收有明显的差异。研究表明:辐射诱导的癌细胞生物效应可以通过单细胞红外光谱灵敏表征;该方法有可能成为快速检测辐射效应的有效手段。     

头发的同步辐射XRF实验

给出了用同步辐射Ｘ射线荧光分析法测定人发中微量元素含量沿头发长度方向分布的结果。重复扫描单根头发、五根头发的结果表明实验的精密度很好；一个人头部同一区域三根不同头发相应部位大多数元素含量的变化趋势基本相同，并有大体一致的相对比值；四个不同人头发相应部位元素含量的变化趋势是不同的，且有不同的相对比值。     

Angle-resolved photoemission spectroscopy in Hubbard model based on cluster perturbation

Angle-resolved photoemission spectra(ARPES) are calculated in the Hubbard model by using cluster perturbation method. It is found that in a cluster of 12 sites, the local density of states displays the phase transition from normal conductor to Mott insulator with the increase of the electron-electron coupling. We show that a pseudogap develops from the metallic phase to the insulating phase. Evidence of spin-charge separation is also verified in the calculated single particle spectral functions.     

同步辐射光源的发展和现状

综述了同步辐射的特点，同步辐射光源的发展历史和现状。介绍了下一代新光源的设计概念。     

Synchrotron radiation photoionization mass spectrometry of laser ablated species

The present paper describes an experimental apparatus suitable to create and study free clusters by combining laser ablation and synchrotron radiation. First tests on sulfur samples, S, showed the production, through laser ablation, of neutral S_n clusters (n = 1–8). These clusters were ionized using synchrotron radiation at photon energies from 160 eV to 175 eV, across the S 2p core edge. The feasibility of such combined ablation–synchrotron radiation experiments is demonstrated, opening new possibilities on the investigation of free clusters and radicals.     

Synchrotron radiation studies of additives in combustion I: Water

Small Angle X-ray Scattering (SAXS) measurements have been performed on a partially pre-mixed ethylene-air flame with and without the introduction of a water aerosol for the same flame height. Our measurements are sensitive to particles with radii in the range of 6-78 nm. It is found that water addition leads to soot suppression below the detection limit at low heights along the flame centerline (<11 mm) and to an increased sooting tendency higher up in the flame. There, larger primary particles (R_g∼20-45 nm) shaped as agglomerates with fractal dimension about 2 are observed together with a large number of smaller (R_g ∼ 10 nm) smooth particles, which we identify with sub-primary units observed in previous work on pure diffusion flames. In the case of the un-doped partially pre-mixed flame, however, only relatively (R_g ∼ 20-35 nm) large spherical particles (Porod’s exponent about 4) are observed. An intriguing result is that water addition induces the enhanced formation of sub-primaries, with these having more than 2 orders of magnitude higher number concentration with respect to the spherical particles in the water free flame.     

Synchrotron radiation X-ray fluorescence analysis on altered mineral muscovite in gold deposit

Synchrotron radiation X-ray fluorescence (SRXRF) microprobe was used to ananlyse altered mineral muscovite and its surrounding feldspar in Yuerya gold deposit. The major, minor and trace elements of the two minerals were detected and analyzed. SRXRF analysis showed that the Yuerya muscovite had a complex chemical composition. containing K, Fe, Ca, Ti, Cr, Mn, Co, Cu, Zn and many trace or ultra-trace elements. Since muscovite resulted from the alteration of hydrothermal ore fluid acting on feldspar (plagioclase), the difference of chemical composition between the two minerals shows the components of ore fluid, which are characterized by the enrichment of alkaline and alkaline-earth metal elements K, Ca and ore-associated elements Fe, Cu, Zn. And gold. silver and platinum, invisible under microscope, were detected in some areas of muscovite but not found in feldspar. Especially platinum, a mantle material is rarely seen in the earth crust but now found in the gold deposit of magmatic sources; its appearance approves the idea of mantle flux participating in the gold mineralization, which suggests that the tectonic event controlling gold mineralization in the Yuerya district is a mantle phenomenon.