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1.
The High Temperature Superconductors are characterized by a very anisotropical structure and by typical arrangements of Cu- and O-atoms within CuO2-planes. In studying the electronic structure of these compounds there is a strong demand for high resolution valence band spectroscopy. Using an electron probe microanalyzer we study the X-ray emission of O-Kga and Cu-L emerging from polycrystalline YBa2Cu3O7 and Tl2Ba2Ca2Cu3O10. The O-K emission band is analyzed using a chlinochlore crystal in (001) orientation (2d = 28.4 Å). For the Cu-L emission band we use a beryl crystal in (10¯10) orientation (2d = 15.9 Å). Furthermore, orientation dependent X-ray emission spectroscopy of single-crystalline YBa2Cu3O7 and Tl2Ba2Ca1Cu2O8 specimens was performed. We present the partial O-K spectra which represent the O-2p ( = x, y, z) electronic densities of states of the valence band and compare them with calculated data. 相似文献
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Michael Meyberg Elvezio Morenzoni Thomas Wutzke Uwe Zimmermann Franz Kottmann Klaus Jungmann Björn Matthias Thomas Prokscha 《Hyperfine Interactions》1994,87(1):1075-1081
At PSI we are investigating the technique of decelerating an existing very intense secondary beam of surface
+ (4 MeV) to an energy of 10 eV using appropriate moderators. These
+ can then be used as a source of a tertiary beam of low energy muons with tunable kinetic energy between 10 eV and 10 keV.With a 1000 A layer of solid Argon deposited on an Al substrate we obtain a moderation efficiency (with respect to the number of incoming surface
+) of the order of 10–4.Results of our investigations and the present status of the project are presented together with future plans and possibilities. 相似文献
3.
Morenzoni E. Birke M. Hofer A. Kottmann F. Litterst J. Matthias B. Meyberg M. Niedermayer Ch. Prokscha Th. Schatz G. Wutzke Th. 《Hyperfine Interactions》1996,97(1):395-406
During the last few decades, a variety of methods has been developed which makes use of polarized positive muons as a microscopic probe of the magnetic properties of condensed matter (muon spin rotation, relaxation, resonance,SR). Until now, available beams for SR studies have delivered 100% polarized muons with energies in the MeV range, resulting in a deep penetration of the muons into the sample material under investigation. This presently limits the applications of theSR technique to the study of the bulk characteristics of matter. To be able to control the implantation depth, a very low energy beam of polarized muons is being developed at the Paul Scherrer Institute. Very slow polarized muons (kinetic energy 10 eV, polarization 90%) are obtained from the moderation of a high energy muon beam in a thin film of an appropriate condensed gas. These muons can be used as a source for a beam of tunable energy between a few tens of eV and some tens of keV. Implantation depths in the range of few to a few hundreds of nanometers can thus be achieved by varying the energy. 相似文献
4.
Franz Effenberger Hariolf Kottmann 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4)
Abstract Aryl phosphonates can be prepared in good yields from the respective arenes and tri- or dialkylphosphites by either chemical or electrochemical oxidation1. The anodic oxidation proceeds either via phosphonium radical cations which then attack the arenes electrophilically or via arene radical cations which add the trialkyl-phosphite as nucleophile1,2. Aryl phosphonates are also obtained in good yields by chemical oxidation with peroxidisulfate/AgNO3, Iron(III)- or Cerium(IV)-complexes in acetonitrile/water or glacial acetic acid3. 相似文献
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Hartmann F. J. Daniel H. Maierl Chr Mühlbauer M. Schott W. Wojciechowski P. Hauser P. Petitjean C. Taqqu D. Kottmann F. Markushin V. E. 《Hyperfine Interactions》1996,101(1):623-632
Two experiments with low-energy muons are described: the determination of the stopping power of C, Si, Ti and Au for muons at energies down to 2 keV and the measurement of the diffusion times for pµ and dµ atoms in low-pressure (0.25–12 hPa) hydrogen gas. A pronounced Barkas effect was found for muons at the Bragg peak (about 10 keV): the stopping power for µ– in C, e.g., is about 30% lower than that for µ+. The mean kinetic energy of pµ atoms at the end of the cascade in 1 hPa hydrogen gas was determined to be (2.6 ± 0.6) eV (preliminary value). 相似文献
7.
Pohl R Daniel H Hartmann FJ Hauser P Kottmann F Markushin VE Mühlbauer M Petitjean C Schott W Taqqu D Wojciechowski-Grosshauser P 《Physical review letters》2006,97(19):193402
The kinetic energy distribution of ground state muonic hydrogen atoms mup(1S) is determined from time-of-flight spectra measured at 4, 16, and 64 hPa H2 room-temperature gas. A 0.9 keV component is discovered and attributed to radiationless deexcitation of long-lived mu p(2S) atoms in collisions with H2 molecules. The analysis reveals a relative population of about 1%, and a pressure-dependent lifetime (e.g., 30.4 +21.4/-9.7 ns at 64 hPa) of the long-lived mu p(2S) population, equivalent to a 2S quench rate in mu p(2S)+H2 collisions of 4.4 +2.1/-1.8 x 10(11) s(-1) at liquid-hydrogen density. 相似文献
8.
Aldo Antognini Franz Kottmann François Biraben Paul Indelicato François Nez Randolf Pohl 《Annals of Physics》2013
The 7σ discrepancy between the proton rms charge radius from muonic hydrogen and the CODATA-2010 value from hydrogen spectroscopy and electron-scattering has caused considerable discussions. Here, we review the theory of the 2S–2P Lamb shift and 2S hyperfine splitting in muonic hydrogen combining the published contributions and theoretical approaches. The prediction of these quantities is necessary for the determination of both proton charge and Zemach radii from the two 2S–2P transition frequencies measured in muonic hydrogen; see Pohl et al. (2010) [9] and Antognini et al. (2013) [71]. 相似文献
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D. Taqqu F. Biraben C.A.N. Conde T.W. Hänsch F.J. Hartmann P. Hauser P. Indelicato P. Knowles F. Kottmann F. Mulhauser C. Petitjean R. Pohl P. Rabinowitz R. Rosenfelder J.M.F. Santos W. Schott L.M. Simons J.F.C.A. Veloso 《Hyperfine Interactions》1999,119(1-4):311-315
The muonic hydrogen atom in the 2s state provides the possibility of achieving high precision laser spectroscopy experiments
from which a high precision value of the proton radius can be deduced. This will ultimately allow an increased precision in
the test of QED in bound systems. Important progress has been made in recent years in the ability to stop muons in a low pressure
gas target and in the understanding of the 2s-metastability in muonic hydrogen. As a consequence the 2s–2p laser spectroscopy
experiment is now feasible and we present here the basic experimental concept considered by our collaboration.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献