X射线连续谱晶体单色器的分辨率

本文讨论了在连续X射线谱的情况下,例如EXAFS谱时,晶体单色器的能量色差。根据连续谱强度随能量变化很小的特点,将其强度看作一常量,提出了计算平晶及Johann,Johansson弯晶单色器平均分辨率的计算方法。同时也指出了以往文献中关于Johann法反射几何分析的一些不当之处。并证明Johann法能得到比过去人们所估计的好得多的分辨率。 关键词：     

前置平面镜热负载对变包含角平面光栅单色器分辨率的影响

针对变包含角平面光栅单色器前置平面镜（PM）受热负载而导致的单色器分辨率降低问题,提出优化聚焦常数（C_ff）补偿分辨率的方法。首先,计算不同C_ff值时PM的热功率吸收谱,在此基础上对镜面热负载进行热-结构耦合分析,得到不同热负载时PM表面热变形的变化量;然后,结合理想分辨率公式和光线追迹软件求出加热负载的单色器分辨率;最后,优化C_ff实现分辨率的补偿。研究结果表明,以软X射线谱学显微光束线站为例,当出射光能量为1 000 eV时,将C_ff由1.8优化至1.84,单色器分辨率即可与无热负载时的相同,该优化方法可有效补偿单色器分辨率的降低。     

不需制备样品与获得期望强度的红外单光束谱

为扣除溶剂或其他背景组分的干扰,测量红外光谱时常常需要获得期望强度的高质量背景单光束谱。通常,实验上获得期望强度的背景谱是极其困难的。为实现这一重要且十分困难的目标,引进了杂化单光束谱的概念。同一溶液但不同厚度的b₁和b₂的两样品的单光束谱分别为Φ_b1和Φ_b2,则定义它们的线性组合Φ_α=αΦ_b1+(1-α)Φ_b2为杂化单光束谱,其中α(0≤α≤1)称为组分因子。调整组分因子α数值,就可以精确调控杂化谱的强度。在合适的条件下,杂化谱Φ_α与厚度为b₂-αb₂+αb₁的真实样品的光谱高度类似,即Φ_b2-αb2+αb1≈Φ_α。因此,不用制备厚度为b₂-αb₂+αb₁的样品,其单光束谱可以用Φ_α来替代。随着α变化,可以得到不同的Φ_α,厚度在b₁和b₂间的真实样品的单光束谱都可用相应的Φ_α来替代。实验结果证实,杂化谱提供了一种简单和易操作的扣除背景干扰的高效方法。     

Johann单色器能量分辨率分析

Johann单色器是一种广泛应用的X光单色器,对其能量分辨率已有若干工作进行过分析.对此问题进行了进一步的分析,改进了已有的工作.将计算结果和已有公式的计算结果同时与SHADOW追迹结果进行比较,理论计算与追迹结果有更好地吻合,同时适用范围更大.     

以新型分子距边矢量ν估计和预测烷烃核磁共振碳谱(13C NMR)化学位移和(CSS)

系统研究了核磁共振碳谱与化学位移和规律,以及分子拓扑指数在定量[结]构[波]谱关系（QSSR）中的应用.本文基于矢量路径长度矢量p=（P₁, P₂, P₃,…, P_m）与分子中原子相互作用,提出了一种新型分子距边矢量并发现它与烷烃¹³C NMR 化学位移和有良好线性相关性, 回归方程及其统计参数为:
CSS=bν+p₃=Σ^m_j=0b_jν_j+b₁₀p₃=b₀ν+b₁ν₁+b₂ν₂+b₃ν₃+b₄ν₄+b₅ν₅+b₆ν₆+b₇ν₇+b₈ν₈+b₉ν9_ν+b₁₀P₃ =-13.6011+22.2133 ν₁+28.4121 ν₂+25.9416 ν₃+26.6709 ν₄+14.4976 ν₅+5.7240 ν₆-5.3830 ν₇-3.2152 ν₈-15.0213 ν₉-25.7099 ν₁₀+12.2786P₃ (n=63, R=0.9970, EV=99.68%, RMS=3.7348, F=2418.2; 交互校验CV为: R=0.9893, EV=98.83%, RMS=7.1261, F=664.046); 结果良好.     

基于新型分子距边矢量ν与多元统计方法对于烷烃13C NMR化学位移和(CSS)估计与预测的深入研究

基于本实验室提出一种新型以势能形式表达的分子距边矢量, 深入地系统研究了核磁共振碳-13谱化学位移和(CSS)规律以及分子拓扑指数矢量在定量结构波谱关系(QSSR)中的应用. 借助多种计量化学方法包括多元线性回归、逐步多元回归、主成分回归、主筛选回归等进行分子拟模和定量相关研究, 发现烷烃¹³C NMR 化学位移和(CSS)与其分子距边矢量及路径长度指数有良好线性相关性, 回归方程及其统计参数为:CSS=bν+cp₃=∑_^mj=0b_jν_j+b₁₁p₃=b₀ν+b₁ν₁+b₂ν₂+b₃ν₃+b₄ν₄+b₅ν₅+b₆ν₆+b₇ν₇+b₈ν₈+b₉ν₉+b₁₀ν₁₀+b₁₁p₃=-13.576+22.179ν₁+28.407ν₂+25 .950ν₃+26.690ν₄+14.498ν₅+5.726ν₆-5.379ν₇-3.214ν₈-15.021ν₉ -25.710ν₁₀+12.278p₃ n=63, R=0.997, EV=99.68%, RMS=3.7348, SD=4.1 18, F= 773.116, U=144228.844, Q=864.938; CV: R²_CV=0.980, EV=98.83%, RMS=7.126 1, SD_CV=7.634, F_CV=221.720, U_CV=142121.891, Q_CV=2971 .896.结果良好.     

DISLOCATION DISSOCIATION ON CLIMB PLANE IN TEXTURED YBa2Cu3O7-δ SUPERCONDUCTOR

Using high resolution electron microscopy, the structure of [100] tilt boundary with misorientation of 1.2° in YBa₂Cu₃O_7-δ has been determined. The boundary is shown to consist of an array of partial dis-locations, These partials result from the dissociation of a perfect dislocation with a Burgers vector [0, 0, c] on its climb plane according to the reaction, b→b₁+b₂+b₁+b₂+b₁+b₂. Here b=[00c], b₁=[O,b/2, c/6} (or [a/2, 0, c/6] ). b₂=[0, -b/2. c/6] (or[ -a/2, 0, c/6] ). The spacing between the perfect dislocations satisfies the Read-Shockley formula. There exist no amorphous phases in the boundary region.     

光诱导细胞色素b5还原反应及机理的光谱学研究

在生命体内有关电子转移的研究备受关注,其中蛋白质以及酶之间的电子转移研究已成为热点,目前有关光诱导血红素蛋白还原的详细机理尚不明确,电子转移也许是解释这一机理的有效途径。通过紫外-可见吸收光谱、稳态荧光光谱和圆二色等光谱系统地研究了体外近生理溶液环境中,不同的紫外定波长、pH、游离氨基酸、谷胱甘肽、咪唑对Cyt b₅光照还原的影响,以阐明Cyt b₅不能用传统提出的机制去解释的光还原机制。结果表明: 在近紫外区通过直接的光激发高铁细胞色素b₅ (Cyt b₅)可以使其被还原成亚铁Cyt b₅,经过分析发现了Cyt b₅被光还原的机制和促进条件。用280 nm单色光照射Cyt b₅溶液,发现随着光照时间的延长,Cyt b₅溶液紫外-可见光谱中Soret带由412 nm红移到421 nm,Q带556 nm处吸收峰逐渐增强。Cyt b₅被光照后发生了类似化学还原剂作用的还原反应,同时发现了不同的光照波长、不同的pH、氨基酸种类以及各种其他配体等存在下对Cyt b₅的还原程度影响不同。采用280 nm波长、在偏碱性条件下光照Cyt b₅时还原程度最强;溶液中加入谷胱甘肽和咪唑能通过提供电子和氢供体途径促进Cyt b₅的光照还原反应发生;溶液中游离Met的存在能以最大速率促进光照还原反应的发生。基于以上结果提出Cyt b₅光还原的机理是从卟啉环到三价铁的电子转移,通过280 nm激发形成卟啉π阳离子基团和亚铁。采用稳态荧光光谱和圆二色谱对Cyt b₅光照还原发生前后进行检测,发现光诱导蛋白发生还原后,Cyt b₅主链结构逐渐伸展,二级结构发生了一定改变,α-螺旋含量逐渐降低,β-折叠含量逐渐升高,但是整个Cyt b₅的二级结构仍以α-螺旋为主。该研究结果不仅对了解光对含血红素蛋白（酶）的结构和功能的影响有重要的理论和实践意义,而且对于生命体内的氧化还原反应和电子传递机制提供一定理论依据。     

具有D4h对称性构型的C2+4分子的Jahn-Teller效应与能级分裂

依据量子理论与配位场理论,利用群论和对称性分析的方法探讨了C²⁺₄分子在具有D_4h对称性构型时,E×(b_1g+b_2g)系统的Jahn-Teller效应中的相关问题.研究了C²⁺₄分子的电子态与声子态的对称性及其活跃声子态,讨论了系统声子间的耦合与CG系数,构建了E×(b_1g+b_{2g 关键词： 2+4分子')" href="#">C²⁺4分子 对称性 能级分裂 Jahn-Teller畸变}     

弧矢聚焦双晶单色器性能的提高

本文从理论上分析了聚焦双晶单色器的双晶在不同方向偏离理想位置所引起的双晶Bragg角偏差Δθ,为设计研制单色器双晶的安装精度或微动调试精度提供了理论依据,从而达到提高单色器性能的目的.     

The use of asymmetric reflection for control of the effective distance between monochromator and X-ray source

Formulae of the dependence of the effective distance between an asymmetric crystal monochromator and an X-ray source on the monochromator’s asymmetry parameter have been obtained for the cases of characteristic and synchrotron radiations.     

A sagittally focusing double‐multilayer monochromator for ultrafast X‐ray imaging applications

The development of a sagittally focusing double‐multilayer monochromator is reported, which produces a spatially extended wide‐bandpass X‐ray beam from an intense synchrotron bending‐magnet source at the Advanced Photon Source, for ultrafast X‐ray radiography and tomography applications. This monochromator consists of two W/B₄C multilayers with a 25 Å period coated on Si single‐crystal substrates. The second multilayer is mounted on a sagittally focusing bender, which can dynamically change the bending radius of the multilayer in order to condense and focus the beam to various points along the beamline. With this new apparatus, it becomes possible to adjust the X‐ray beam size to best match the area detector size and the object size to facilitate more efficient data collection using ultrafast X‐ray radiography and tomography.     

Performance and application of a high energy monochromated Cu Kα1 X-ray source for the electron spectroscopy of materials

A Cu Kα₁ sealed tube X-ray source (hν = 8047.8 eV) and LiF(2 2 0) Johansson geometry monochromator crystal have been interfaced to a Scienta ESCA300 spectrometer for high energy XPS studies of materials, in particular for the measurement of Auger parameters associated with deep core levels in metallic alloys. The detailed arrangement of the source, monochromator and spectrometer combination is described, and factors affecting the overall intensity and resolution are discussed. The optimisation and characterisation of the system are also described. Several examples of Cu Kα₁ excited survey spectra (Cr, Fe, stainless steel), deep core level spectra (Cr 1s, Fe 1s) and Auger spectra (Cr KLL, Cr LMM, Fe KLL) are presented, which illustrate the capability of the system. Auger vacancy satellites are identified in the Cr LMM spectrum. For a series of Cr–Si alloys measurements are reported of the change in the Cr Auger parameter on going from metal to alloy.     

High‐power‐load DCLM monochromator for a computed tomography program at BMIT at energies of 25–150 keV

The research program at the biomedical imaging facility requires a high‐flux hard‐X‐ray monochromator that can also provide a wide beam. A wide energy range is needed for standard radiography, phase‐contrast imaging, K‐edge subtraction imaging and monochromatic beam therapy modalities. The double‐crystal Laue monochromator, developed for the BioMedical Imaging and Therapy facility, is optimized for the imaging of medium‐ and large‐scale samples at high energies with the resolution reaching 4 µm. A pair of 2 mm‐thick Si(111) bent Laue‐type crystals were used in fixed‐exit beam mode with a 16 mm vertical beam offset and the first crystal water‐cooled. The monochromator operates at energies from 25 to 150 keV, and the measured size of the beam is 189 mm (H) × 8.6 mm (V) at 55 m from the source. This paper presents our approach in developing a complete focusing model of the monochromator. The model uses mechanical properties of crystals and benders to obtain a finite‐element analysis of the complete assembly. The modeling results are compared and calibrated with experimental measurements. Using the developed analysis, a rough estimate of the bending radius and virtual focus (image) position of the first crystal can be made, which is also the real source for the second crystal. On the other hand, by measuring the beam height in several points in the SOE‐1 hutch, the virtual focus of the second crystal can be estimated. The focusing model was then calibrated with measured mechanical properties, the values for the force and torque applied to the crystals were corrected, and the actual operating parameters of the monochromator for fine‐tuning were provided.     

激光等离子体球面晶体光谱成像

 利用自聚焦原理,研制了一种新型的球面弯晶谱仪。晶体分析器采用云母材料,其弯曲半径为380 mm,布拉格角为51°。利用成像板接收光谱信号,其有效面积为30 mm×80 mm,从等离子体源经晶体到成像板的光程长为980 mm。物理实验在中国工程物理研究院激光聚变研究中心20 J激光装置上进行,入射激光能量为6.78 J,成像板获得了铝激光等离子体X射线的光谱空间分辨信号。球面云母弯晶谱仪的光谱分辨率达到1 000～1 500,在相同环境放置的PET平晶的光谱分辨率为50～100。结果表明：球面弯晶具有较高的光谱分辨率和信噪比,适合于激光等离子体X射线的光谱学研究。     

A possibility of parallel and anti-parallel diffraction measurements on neutron diffractometer employing bent perfect crystal monochromator at the monochromatic focusing condition

In a conventional diffractometer having single monochromator, only one position, parallel position, is used for the diffraction experiment (i.e. detection) because the resolution property of the other one, anti-parallel position, is very poor. However, a bent perfect crystal (BPC) monochromator at monochromatic focusing condition can provide a quite flat and equal resolution property at both parallel and anti-parallel positions and thus one can have a chance to use both sides for the diffraction experiment. From the data of the FWHM and the Δd/d measured on three diffraction geometries (symmetric, asymmetric compression and asymmetric expansion), we can conclude that the simultaneous diffraction measurement in both parallel and anti-parallel positions can be achieved.     

Pseudo Stark and uniaxial stress splitting of the 6955 Å zero-phonon line in LiF

The spectral resolution of quartz crystals bent to a cylindrical form by means of four rods was investigated with CuKα radiation in a reflection type arrangement. The crystal adjustment was made optically using interference fringes. With the crystal bent to a circular cylinder the deviations from exact focusing inherent to the Johann case could be measured and were found to be in agreement with theory. — Crystals bent to a logarithmic spiral have also been studied. With a 24 mm broad reflecting area (mean radius of curvature 1 m; (13¯40)-plane) an uncorrected full width at half maximum intensity of 0.43 XU or 2.25 eV was observed for the CuKα ₁ line, in agreement with double crystal spectrometer measurements.     

软X射线直线单色仪光场分布实验研究

合肥国家同步辐射光源软X射线直线单色仪配备三种不同参数的波带片和针孔光阑,通过调节波带片和针孔光阑间的距离可输出1.97—5.44nm波段的软X射线.利用高分辨正性光刻胶,记录了CZP₃₂和30μm针孔光阑组合下的准确聚焦和大离焦量时的软X射线衍射图,即直线单色仪输出的光场分布.获得了有关爱里斑及空间相干半径等实验数据,所得结果与理论计算相一致. 关键词：     

A microfocus X‐ray fluorescence beamline at Indus‐2 synchrotron radiation facility

A microfocus X‐ray fluorescence spectroscopy beamline (BL‐16) at the Indian synchrotron radiation facility Indus‐2 has been constructed with an experimental emphasis on environmental, archaeological, biomedical and material science applications involving heavy metal speciation and their localization. The beamline offers a combination of different analytical probes, e.g. X‐ray fluorescence mapping, X‐ray microspectroscopy and total‐external‐reflection fluorescence characterization. The beamline is installed on a bending‐magnet source with a working X‐ray energy range of 4–20 keV, enabling it to excite K‐edges of all elements from S to Nb and L‐edges from Ag to U. The optics of the beamline comprises of a double‐crystal monochromator with Si(111) symmetric and asymmetric crystals and a pair of Kirkpatrick–Baez focusing mirrors. This paper describes the performance of the beamline and its capabilities with examples of measured results.