Results 1 - 10 of 3475
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[en] The influence of diffracting conditions on electron energy loss spectroscopy (EELS) was determined by measuring the relative intensity ratio I/sub K//sup A/(β,delta)/I/sub O/(β,Δ) as a function of the deviation parameter s, where the first term is the intensity of electrons which have excited the K/sup th/ inner shell level and the second term is the total transmitted intensity measured over an energy window Δ and an acceptance angle β. Measurements were done on an electropolished single crystal specimen of V. The results of the experiment were in good quantitative agreement with similar experiments performed on the C K-edge in graphite and the N K-edge in A1N. The pronounced oscillations in the partial ionization cross section for (/s/>0 in the A1N work were not observed in this work. It is concluded that the errors in quantitative EELS are minimized at values of /s/>>O using non-zero incident beam divergence and at specimen thicknesses t is not equal to epsilon/sub g//2. These errors are seen as being most significant during absolute quantification, and an equation is proposed to reduce the errors
[en] Mathematical formulae, theories and examples of application of the addition, mixing and diluting methods. The simple method of addition can only be applied to prevent interelementary effects if a linear calibration curve is available. Should this not be the case, other methods of dilution and mixing must be used. The simple mixing of sample and standard seems a practically favourable method. It is described besides other methods and explained by means of an example. The estimation of the analytic error is possible without a lot of calculation. The method of simple mixing can only be used with completely mixable substances. It can then, however, be used when either no programmed computer for the matrix correction is available or if there are no calibration standards which can be used to produce a calibration curve or to determine the matrix correction coefficients. (orig./HP)
[de]Mathematische Formeln, Theorie und Anwendungsbeispiele der Additions-, Mischungs- und Verduennungsmethoden. Die einfache Additionsmethode ist zur Ausschaltung von Interelementeffekten nur anwendbar, wenn eine lineare Eichkurve vorliegt. Ist dies nicht der Fall, muessen andere Methoden der Verduennung und Zumischung verwendet werden. Als praktisch guenstigstes Verfahren erscheint die einfache Mischung von Probe und Standard. Sie wird, neben anderen Verfahren, beschrieben und an einem Beispiel erlaeutert. Die Abschaetzung des Analysenfehlers ist ohne grossen Rechenaufwand moeglich. Die Methode der einfachen Mischung ist nur bei voellig mischbaren Substanzen anwendbar. Sie bietet sich aber dann an, wenn entweder kein programmierter Rechner fuer die Matrixkorrektur zur Verfuegung steht oder wenn keine Eichstandards vorliegen, die zur Herstellung einer Eichkurve oder zur Bestimmung der Matrix-Korrekturkoeffizienten benutzt werden koennen. (orig./HP)
[en] For examples with special elemental composition the so-called enhancement effect must be considered. The X-ray yield of a line energetically below a very intense line in a spectrum may be in the sample than is the case. This effect is investigated for high energy projectiles such as 30 MeV α-particles theoretically dependent on the X-ray energies, the elemental abundances and the target thickness. Further on the projectile energy dependence is discussed. For an experimental check three thick Fe samples containing Cr and Mn are measured. For a small admixture of e.g. Cr in a Fe matrix the analysis results can differ by a factor of about 2. In the PIXE analysis of objects, in which the exciting radiation of the main elements has an energy just above the X-ray absorption edge of a minor element, the enhancement effect is not to be neglected. (orig.)
[en] It is demonstrated that enhancement-absorption effects which perturb the quantitative feature of PIXE can be lowered by using liposomes (synthetic phospholipid bilayer vesicles) as homogenizers in the preparation of thin targets. (orig.)
[en] In connection with ideas to produce undulator-like radiation in the hundreds of keV up to the MeV region by means of positron and electron channeling, there is renewed interest to study various channeling phenomena also experimentally. With electrons experiments have been performed at the Mainz Microtron MAMI to explore channeling-radiation emission by a 4-period epitaxially grown strained layer Si1.xGex undulator with a period length of λu = 9.9 μm. Unfortunately, high-quality positron beams of sufficient intensity are not easily accessible. The only serious candidate in Europe seems to be the Beam Test Facility (BTF) at INFN/LNF, Frascati, Italy. Some requirements to extent BTF in a facility which is also well suited for positron channeling-radiation experiments will be outlined.
[en] Numerous techniques of analysis and surfaces and thin films characterization have been developed in the last twenty years. This paper presents the possibilities and the limitations of LEEIXS spectrometry, and its application to the atomic and molecular characterization of the surface of various metals. 19 refs., 22 figs
[fr]De nombreuses techniques d'analyse et de caracterisation des surfaces et des films minces ont vu le jour depuis vingt ans. Cet article traite des possibilites et des limites de la spectrometrie LEEIXS et de son application a la caracterisation atomique et moleculaire de la surface de differents materiaux
[en] The proton induced x-ray emission technique has been used for the characterisation of obsidian samples from the S.W. Pacific region (Papua New Guinea, New Hebrides, New Zealand). It is intended to build up a reference library of data so that the origins of artefacts may be traced
[en] Natural heterogeneous lapis lazuli has been investigated using the complementary techniques of ionoluminescence spectroscopy, ionoluminescence microscopy and micro-PIXE. The equivalent probed depths, the possibility of simultaneous use and the capability of non-destructive in-air application suggest the combined use of ionoluminescence and micro-PIXE techniques as an appropriate approach in mineral analysis to reveal the texture, chemical composition, and elemental distribution of the samples. In this research work, the various mineral phases of a lapis lazuli sample were detected and analyzed. It was possible to identify most of the minerals in the analyzed area, including apatite, a mineral phase uncommon in lapis lazuli, and point out different luminescence features of crystals of the same mineral, diopside, found in different parts of the same lapis lazuli sample.