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EXRS 2006 – BOOK OF ABSTRACTS ORAL PRESENTATIONS 1 2 INV-1 X-RAY STANDARDS: FROM X-RAY TUBES TO HIGHLY-CHARGED IONS. Paul Indelicato Laboratoire Kastler Brossel -Ecole Normale Supérieure, Département de Physique 24 Rue Lhomond, F-75231 Paris CEDEX 05 Université P. et M. Curie, Pyramide 14-24, Case 74, 4 place JussieuF-75252 Paris Cedex 05, France X-ray standards, i.e, X-ray line energies or wavelengths measured with the highest possible accuracy, have applications in many fields of physics. One can cite field as different as crystallography as well as medium energy particle physics. Current X-ray standards are based upon X-ray lines emitted by solid targets excited by electron bombardment or fluorescence. These lines are not very well suited for X-ray standards: they are broad and asymmetric because of the unavoidable presence of many vacancies (shake-off,…) and of auto-ionization. Their energy can only be obtained by direct measurement, and depends on the exact composition of the target surface (chemical shift) and on the instrumental resolution (because of the asymmetry). Their width is much larger than the resolution of the best spectrometers. Many known lines have been measured only once very long ago, in an uncontrolled environment. A complete survey of the current status of X-ray line energies and associated problems can be found in [1]. Several attempts have been made to remedy some or all of these problems and find better candidates. Recently low energy gamma rays have been advocated for such applications [2]. They are narrow transitions of nuclear origin, but are indeed difficult to manipulate (strong radioactive sources are needed), there are very few suitable lines, and the energy cannot be predicted. More recently X-rays from exotic atoms and highly charged ions have been used. Exotic atoms are atoms in which most or all electrons have been replaced by one unstable particle. Although their production is difficult, progress in accelerator, spectrometer and production techniques have enabled a reasonable use [3]. Highly charged ions are the most promising technique. Very narrow and intense transitions produced by an Electron-Cyclotron Resonance Ions source have been observed [4] and used [5] to characterize in detail an X-ray spectrometer and measure very accurately the energy and width of pionic hydrogen, a system of interest for the study of strong interaction. In this talk I will provide a review of the current problems and perspectives in this field. I will describe ongoing experiments in our laboratory intended to provide the first X-ray standard from highly charged ions. [1] X-ray transition energies: New approach to a Comprehensive evaluation, R.D. Deslattes, E.G. Kessler Jr., P. Indelicato et al. Reviews of Modern Physics 75, 35-99 (2003). [2] Ȗ-Ray Wavelength Standard for Atomic Scales, Y.V. Shvyd'ko, M. Lerche, J. Jäschke et al. Physical Review Letters 85, 495-498 (2000). [3] Low-energy X-ray standards from hydrogenlike pionic atoms, D.F. Anagnostopoulos, D. Gotta, P. Indelicato et al. Physical Review Letters 91, 240801 (2003). [4] High Resolution He-like Argon And Sulfur Spectra From The PSI ECRIT, M. Trassinelli, S. Biri, S. Boucard et al., ELECTRON CYCLOTRON RESONANCE ION SOURCES: 16th International Workshop on ECR Ion Sources ECRIS'04, Vol. 749, AIP (Berkeley, California (USA)) pp 81-84, (2005). [5] On the characterisation of a Bragg spectrometer with X-rays from an ECR source, D.F. Anagnostopoulos, S. Biri, D. Gotta et al. Nuclear Instruments & Methods in Physics Research, Section A (Accelerators, Spectrometers, Detectors and Associated Equipment) 545, 217 (2005). Email: [email protected] 3 O1-1 DOUBLE K-SHELL PHOTOIONIZATION OF MAGNESIUM AND ALUMINIUM J.-Cl. Dousse1, M. Berset1, W. Cao1, K. Fennane1, J. Szlachetko1 M. Szlachetko1, J. Hoszowska2 1Department of Physics, University of Fribourg, CH-1700 Fribourg, Switzerland 2European Synchrotron Radiation Facility (ESRF), F-38043 Grenoble, France We report on measurements of the K-hypersatellite fluorescence x-ray emission of solid Mg and Al. The experiments were performed at the European Synchrotron Radiation Facility by means of high-resolution x-ray spectroscopy, using a von Hamos curved crystal spectrometer [1]. The diagram and hypersatellite x-ray spectra of Mg were measured at 9 different photon beam energies between 2746 eV and 3947 eV. The onset energy for the production of the double 1s vacancy states was found to lie at about 2750 eV. Above the threshold energy, a fast rise of the hypersatellite intensity with the excitation energy is observed but then the hypersatellite yields tend toward a saturation value, as predicted by the model of Thomas [2]. At saturation, the relative hypersatellite yield was found to be about one order of magnitude bigger than theoretical predictions based on the sudden approximation model. For the energy shift of the hypersatellite with respect to the parent diagram line, a value of 114.28(3) eV was obtained, in good agreement with the result of 114(1) eV deduced from a previous heavy-ion experiment [3]. Furthermore, the Lorentzian width of the hypersatellite transition predicted by theory underestimates significantly the value obtained from our measurements. To verify whether the discrepancies observed for Mg are specific to this element or also affect other low-Z atoms, the hypersatellite measurements were extended recently to Al. The hypersatellite transition was observed for 11 different photon beam energies ranging from 3186 eV (onset energy) up to 5451 eV (saturation). Because for Al the hypersatellite line is overlapping with the second order L-satellite of the KE transition, the latter was measured at a beam energy of 3122 eV, i.e. below the hypersatellite onset energy, and its normalized intensity subtracted from the hypersatellite yield at each higher excitation energy. The data analysis is still in progress but preliminary fits show that the hypersatellite yields of Al are also strongly underestimated by the theory. [1] J. Hoszowska et al., Nucl. Instrum. Meth. Phys. Res. A 376, 129 (1996). [2] T.D. Thomas, Phys. Rev. Lett. 52, 417 (1984). [3] M. Kobal et al., Phys. Rev. A 70, 062720 (2004). E-mail: [email protected] 4 O1-2 BROADENING OF DIFFRACTION PROFILE CAUSED BY SURFACE STRESS GRADIENT AND ITS STUDY BY FOURIER ANALYSIS J.T. Assis, V.I.Monin, S.A.Philippov, S.M.Iglesias IPRJ/UERJ, Rio de Janeiro, Brazil It has been shown earlier that strong stress gradient arising on the surface of materials after some superficial treatment causes diffraction line broadening. The interest to study this broadening is connected with the possibility to obtain important information about parameters of stress gradient using X ray diffraction methods. Fourier analysis, widely used in different fields of modern physics, can be applied to study this kind of distortions of diffraction profile. In the present paper the convolution and the deconvolution concepts of Fourier analysis were applied to determine stress distribution function that is responsible for the broadening of diffraction line. The developed methodology was tested by computer simulation of diffraction experiment with linear and exponential stress distribution functions. It was obtained good agreement between original and calculated functions. E-mail: [email protected] 5 O1-3 THE ENERGIES AND RELATIVE INTENSITIES OF L AND M LINES IN THE LOW-ENERGY RANGE Ralf Terborg, Dieter Weirauch Bruker AXS Microanalysis GmbH, Schwarzschildstr. 12, 12489 Berlin, Germany A lot of the publications about fundamental parameters are from the 70s. Within recent years some new atomic databases were published in the internet. These contain – besides other fundamental parameters – line energies and intensities of K, L and M X-ray lines. However, these databases as well as the publications show considerable differences, a lack of accuracy, e.g. line intensities which are varying by three orders of magnitude, and missing lines when compared to measured spectra, especially for the low energy range. This is also true for some widely used but old publications. These discrepancies, especially in the relative line intensities, cannot be explained only by errors in the measurements or uncertainties of depending fundamental parameters. As a matter of fact, line energies and intensities were interpolated or even estimated as roughly constant for a wide range of elements in the periodic system. Additionally, some significant lines like the M-zeta line were neglected in the databases or publications. Even for elements with M line energies greater than 2 keV atomic databases show significant differences. For example, for a common element such as gold some databases show only three lines which agree with experimental spectra in line energy and intensity, whereas at least five lines are significant and clearly visible in experimental spectra. In cooperation with Prof. Wendt of the Institute for Physical High Technology Jena, L and M line spectra were investigated and extended. Results of this work will be presented and some examples will be compared with other databases and publications. Email: [email protected] 6 O1-4 DOUBLE 1S PHOTOINIZATION OF Ca AND V BEYOND MAXIMUM J. Hoszowska1, J.-Cl. Dousse2, M. Berset2, W. Cao2, K. Fennane2 M. Kavic2, J. Szlachetko2, M. Szlachetko2 1European Synchrotron Radiation Facility (ESRF), F-38043 Grenoble, France 2Department of Physics, University of Fribourg, CH-1700 Fribourg, Switzerland The single-photon two-electron process serves as one of the most sensitive probes of electron- electron correlations. Following the absorption of the primary photon two dominant double ionization mechanisms produce "hollow atoms”, namely the electron-electron scattering (knock-out KO) and the shake process [1]. Shake prevails at high photon energies, while knock-out dominates at low energies and falls rapidly with increasing excitation energy to become negligible in the asymptotic regime. Thus, exploring the energy dependence of the 1s double ionization probability permits to investigate the initial-state correlations important for shake and the final-state electron-electron correlations governing the dynamics of the electron impact ionization (KO).