Diffraction filters based on polyimide and poly(ethylene naphthalate) track membranes

The problem of optical filters for soft x rays and extreme ultraviolet that provide a high degree of blocking ultraviolet and visible background radiations is considered. The subject of discussion is the filter based on a track membrane, a polymer film with micrometer and submicrometer pores, rather than the standard thin-film system. It is proposed that the membranes be made of poly(ethylene naphthalate) or polyimide, the UV absorption edge of which lies near the boundary of the visible range. The properties of poly(ethylene naphthalate) and polyimide membranes are contrasted with those of conventional porous poly(ethylene terephthalate) films, which are obtained by ion track etching. The spectral characteristics of poly(ethylene naphthalate) and polyimide films, as well as the formation of “track” pores when the specimens are successively treated by fast ions and chemicals, are studied. The basic parameters of the resulting porous structures are examined, and treatment conditions under which desired optical properties of the membranes are achieved are found. Filters based on poly(ethylene naphthalate) and polyimide track membranes may be applied in x-ray astronomy as constituents of detectors incorporated into solar telescopes and in experiments with the laboratory plasma.     

X-ray diffraction on denatured ferritin

Denatured ferritin, in contrast to other denatured corpuscular proteins, gives several diffractions, even in the regiond>15 Å. These diffractions correspond to the mutual arrangement of the micelles and proteinic component of ferritin. Diffractions in the regiond<15 Å correspond both to the internal structure of the denatured proteinic component — apoferritin — and to the internal structure of ferric micelles of ferritin. Regions containing only the denatured proteinic component with polypeptide chains in-configuration, occur in the structure of denatured ferritin in addition to the crystallites or crystalline regions with regular arrangement of micelles and the proteinic component.

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, , d>15 Å. . d<15 Å — , — . , gb-.

     

德拜对多晶X射线衍射的研究

简述了德拜的生平,回顾了他在多晶X射线衍射研究过程中所作的工作,并分析了他取得成功的因素,展现了他独特的人格魅力.     

Structure of metal nanowires in nanoporous alumina membranes studied by EXAFS and X-ray diffraction

The structure of nanowires of different metals grown within nanoporous alumina membranes has been studied by EXAFS, WAXS and high energy X-ray diffraction. Nanowires of gold, silver, copper and iron adopt the lattice structure and bond distances of the bulk metals. Cobalt nanowires on the other hand were composed of a mixture of hcp phase, stable at room temperature, and fcc phase, which in bulk cobalt is normally stable only at high temperatures, in a ratio depending on the pore size. The nanowires are non-continuous but are made of nanocrystallites whose shape and size was found to depend strongly on the metal. All the metals except gold showed the presence of a preferred orientation which was slight in the case of Ag and Cu but much stronger in the case of iron and cobalt nanowires. Received 30 November 2000     

Optical transparency of makrofol nuclear track filters

Makrofol polycarbonate—one of the widely used materials for making nuclear track filters, has been studied for its transparency to light (Λ = 350 nm to 950 nm). Also the optical transmission and IR-spectroscopy results on the Makrofol foils, forming nuclear track filters by irradiating with 14 MeV/n ²³⁸U ions, with and without post-irradiation UV and γ-exposures, are presented. Studies have been extended to these filters to investigate the variation of percentage transmission with etch-time, pore diameter, at different values of Λ.     

X-ray diffraction on chlorine adsorbed on graphite

Cl₂ layers adsorbed on Grafoil have been investigated by X-ray diffraction between 78 and 285 K. Mono- and submonolayers crystallize in a parallelogram lauttce, incommensurate with the (001) graphite surfaces, the molecules oriented almost perpendicular to the surface. The structure is closely related to that of the (001) planes of three-dimensional solid chlorine. For coverages above the monolayer completion bulk crystalization sets in.     

X-ray resonant powder diffraction

X-ray resonant diffraction can be applied in structural chemistry studies on powder samples. It enables an important limitation of powder diffraction to be overcome. This limitation is related to the low ability of powder diffraction to differentiate elements with close atomic numbers when they occupy the same or close crystallographic sites (mixed occupancy case) and also to discriminate cations with different valence states in different sites. However the resonant effect usually has a second order influence on the measured intensity. As a consequence, the efficiency of this method directly implies the need for excellent quality data collection and has generally been better assessed on elements present in single phase powder samples. In recent years, instrumental developments have been made in synchrotron radiation facilities which allow easier use of resonant powder diffraction for site-specific contrast and valence i.e. oxidation state analyses. Moreover, resonant contrast diffraction tools also have been proposed for better visualization of the anomalous effect both in direct and reciprocal space by using differences between electron density maps or diffraction patterns. Finally the potentialities of this technique for de novo structure solution on macromolecular systems are mentioned.     

软X射线多层膜与衰减膜研究

 本文采用随机数的方法，发展了一种普适的多层膜设计方法，这种方法除可设计一般的周期多层膜，更重要的是它可以根据选定的评价因子，设计不同要求的非周期多层膜。用磁控溅射方法完成软X射线多层膜制备，X射线衍射、卢瑟福背散射、俄歇电子谱和反射率的相对测试用来表征多层膜结构和特性，所得结果说明多层膜的结构完整，周期参数正确。用离子束溅射方法成功地制备了有一定反射率和透过率的软X射线半反半透分束镜；分析了Ag和Zr衰减膜中的杂质含量与分布及其对衰减膜特性的影响，并对衰减系数进行了修正，为实验提供优质的衰减膜。     

软X射线多层膜与衰减膜研究

本文采用随机数的方法,发展了一种普适的多层膜设计方法,这种方法除可设计一般的周期多层膜,更重要的是它可以根据选定的评价因子,设计不同要求的非周期多层膜。用磁控溅射方法完成软X射线多层膜制备,X射线衍射、卢瑟福背散射、俄歇电子谱和反射率的相对测试用来表征多层膜结构和特性,所得结果说明多层膜的结构完整,周期参数正确。用离子束溅射方法成功地制备了有一定反射率和透过率的软X射线半反半透分束镜;分析了Ag和Zr衰减膜中的杂质含量与分布及其对衰减膜特性的影响,并对衰减系数进行了修正,为实验提供优质的衰减膜。     

X-ray Bragg diffraction on periodic surface gratings

We report on the X-ray Bragg diffraction analysis of periodic surface gratings on (100) GaAs crystals. We show that the X-ray Bragg diffraction is a very powerful method to investigate ultrafine surface gratings and allow us to determine not only the grating period but, in particular, the width of the grooves and to characterize the quality of the sidewalls, which is not easily possible with optical methods. The X-ray diffraction on surface crystal gratings is analogue to the Fraunhofer diffraction of multiple slits or reflection gratings.     

A relation between X-ray diffraction based liquid structure and packing coefficient

A relation between the liquid structure and the molecules packing coefficient has been derived on the grounds of the experimental results of X-ray diffraction studies. The packing coefficientk was assumed to be a criterion of correctness of the structural models of 2-methyl-1-propanol and 2-methyl-2-propanol based on experimental results. This coefficient was estimated from the specific volumes of moleculesV ₀, volumes of elementary pseudocellsV and the number of molecules comprised into these pseudocells. The volumesV of pseudocells were estimated from the same X-ray diffraction pattern as was used for determination of the liquid structure. The determined values of the packing coefficient support the chain-like structure of associates of liquid 2-methyl-1-propanol and reject the chain-like structure for liquid 2-methyl-2-propanol.     

SHI induced nano track polymer filters and characterization

Swift heavy ion irradiation produces damage in polymers in the form of latent tracks. Latent tracks can be enlarged by etching it in a suitable etchant and thus nuclear track etch membrane can be formed for gas permeation / purification in particular for hydrogen where the molecular size is very small. By applying suitable and controlled etching conditions well defined tracks can be formed for specific applications of the membranes. After etching gas permeation method is used for characterizing the tracks. In the present work polycarbonate (PC) of various thickness were irradiated with energetic ion beam at Inter University Accelerator Centre (IUAC), New Delhi. Nuclear tracks were modified by etching the PC in 6N NaOH at 60 (±1) °C from both sides for different times to produce track etch membranes. At critical etch time the etched pits from both the sides meet a rapid increase in gas permeation was observed. Permeability of hydrogen and carbon dioxide has been measured in samples etched for different times. The latent tracks produced by SHI irradiation in the track etch membranes show enhancement of free volume of the polymer. Nano filters are separation devices for the mixture of gases, different ions in the solution and isotopes and isobars separations. The polymer thin films with controlled porosity finding it self as best choice. However, the permeability and selectivity of these polymer based membrane filters are very important at the nano scale separation. The Swift Heavy Ion (SHI) induced nuclear track etched polymeric films with controlled etching have been attempted and characterized as nano scale filters.      

Soft X-ray resonant magnetic diffraction

We have conducted the first soft x-ray diffraction experiments from a bulk single crystal, studying the bilayer manganite La2-2xSr1+2xMn2O7 with x=0.475 in which we were able to access the (002) Bragg reflection using soft x rays. The Bragg reflection displays a strong resonant enhancement at the L(III) and L(II) manganese absorption edges. We demonstrate that the resonant enhancement of the magnetic diffraction of the (001) is extremely large, indeed so large that it exceeds that of the nonresonant Bragg diffraction. Resonant soft x-ray scattering of 3d transition metal oxides is the only technique for the atomic selective measurement of spin, charge, and orbital correlations in materials, such as high temperature superconductors, colossal magnetoresistance manganites, and charge stripe nickelates.     

Determination of the crystallographic texture of sintered PrFeB magnets based on X-ray diffraction patterns

An alternative method for determining the degree of crystallographic alignment (cos Θ) of the magnetic Pr₂Fe₁₄B phase (Φ) is proposed. The method is based on the relative X-ray diffracted intensities of the Φ planes of sintered magnets with and without texture. The degree of crystallographic alignment is also determined by X-ray pole figures using the (0 0 4) reflection and considered as a standard reference for comparison. The method is applied to Pr₁₆Fe₇₆B₈ magnets with 0.51cos Θ0.97. The difference between the crystallographic alignments determined by these two methods is 3% within the experimental error. The advantages and limitations of using X-ray diffraction patterns to quantitatively evaluate the texture of sintered magnets are also discussed.     

X光衍射实验的改进与校正

用X射线衍射仪做定量分析衍射实验，会出现因盖革计数器存在分辨时间而漏计的现象．为了简便地测定分辨时间，本文利用单层膜二次照射技术，导出了用来校正积分强度的近似公式，并与逐点校正法作了对比分析，二者符合很好．     

X射线衍射进展简介

100年前,劳厄等证明X射线对硫酸铜晶体具有衍射能力,揭开了X射线衍射分析晶体结构的序幕.100年的发展,X射线衍射已经成为自然科学乃至医学、考古、历史学等众多学科发展的必备技术.文章介绍了X射线衍射现象的发现历史,X射线运动学和动力学理论的发展概况,并举例说明了X射线衍射在粉末多晶体、单晶体和人工功能晶体以及人工薄膜材料中的具体应用情况,最后简要展望了X射线衍射技术的发展前景.     

X射线衍射的发现

简单介绍了埃瓦尔德(Ewald P P)、劳厄(von Laue M)和布拉格父子(Bragg W H及Bragg W L)在1912年发现X射线衍射方面的贡献．1911年埃瓦尔德在索末菲的指导下在慕尼黑大学从事博士论文研究，劳厄在与他的讨论中了解到晶格的平移周期与X射线的波长属于同一量级，因此想到在二维光栅的两个衍射方程组中再加一个类似的方程，就可以描述X射线在三维晶体中的衍射．在此假设的指导下，Friedrieh W和Knipping P在1912年4月开始用CuSO4后来用闪锌矿(立方ZnS)进行实验，很快就得到X射线衍射的证据．这不但证明了X射线的波动性，还确定了晶体的三维周期性．老布拉格在1912年夏得知这个消息，与他儿子小布拉格一道尝试用X射线的粒子性解释它，并由小布拉格在剑桥大学重复这个实验．根据衍射斑点的椭圆形状和从Pope与Below那里学到的晶格理论(由此得知ZnS具有面心立方晶格)，小布拉格将X射线在晶体中的衍射看作是X射线从一些晶格平面的反射，从而推导出著名的布拉格方程．布拉格父子开拓了X射线晶体结构分析这门新兴学科，从简单的无机化合物和矿物，逐渐发展到有机化合物和生物大分子．劳厄和布拉格父子分别强调慕尼黑和剑桥的优良科学环境对发现X射线衍射的重要性．鉴于埃瓦尔德在发现X射线衍射的作用及他后来在倒易格子及动力学衍射理论方面的贡献，不少晶体学家认为他也应获得诺贝尔物理奖．     

用X射线衍射仪验证康普顿效应的实验研究

充分利用多晶X射线衍射仪的衍射、单转、定时计数、叠扫等功能测量数据,采用3种实验测量方法验证了康普顿散射波长的位移公式,分析了不同测量方法对实验结果的影响.     

The effect of X-ray coherence on crystalline diffraction

The importance of respecting the coherent properties of X-rays in the physical interpretation of the profiles of the X-ray diffraction patterns is pointed out. Drawing the analogy between Young's experiment and two-atom X-ray scattering, the author applies the elementary theory of coherence, developed for light optics, to X-ray diffraction by a linear atomic lattice. As his considerations concerning the effect of coherence on diffraction by such a lattice are impossible to verify experimentallly, he tests their correctness by spectrographical measurements of the width of an optical grating diffraction line under different coherence and experimental conditions. The paper is dedicated to the memory of Dr. A. Vaíek, Professor of the J. E. Purkyn University in Brno, who died on November 16, 1966.