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Articles de revues sur le sujet "Electron momentum spectrometer":
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TIXIER, S., Y. ZHENG, T. TIEDJE, G. COOPER et C. E. BRION. « ELECTRON MOMENTUM SPECTROSCOPY OF SURFACES ». Surface Review and Letters 06, no 05 (octobre 1999) : 579–84. http://dx.doi.org/10.1142/s0218625x99000524.
Electron momentum spectroscopy [binary (e,2e) spectroscopy] using transmission geometry is a unique experimental tool for imaging the electron momentum distribution in gas phase samples as well as in thin films. In a solid, the electron momentum distribution is related to the band structure. Development of the (e,2e) technique using a more versatile reflection geometry is attractive since a much wider range of surfaces could be studied. The design of a new reflection (e,2e) spectrometer is presented. It is based on a two-step scattering model in which an incident electron successively reflects and ejects a valence electron from the surface. The scattered and ejected electrons are detected in coincidence and their energies and momentum vectors are simultaneously determined using a high throughput 90° truncated spherical electrostatic analyzer and position-sensitive detectors.
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Wallauer, Robert, Stefan Voss, Lutz Foucar, Tobias Bauer, Deborah Schneider, Jasmin Titze, Birte Ulrich et al. « Momentum spectrometer for electron-electron coincidence studies on superconductors ». Review of Scientific Instruments 83, no 10 (octobre 2012) : 103905. http://dx.doi.org/10.1063/1.4754470.
Itou, Masayoshi, Shunji Kishimoto, Hiroshi Kawata, Makoto Ozaki, Hiroshi Sakurai et Fumitake Itoh. « Development of an (X, eX) spectrometer for measuring the energies of the scattered photon and recoil electron ». Journal of Synchrotron Radiation 5, no 3 (1 mai 1998) : 676–78. http://dx.doi.org/10.1107/s0909049597017913.
The design and performance of a new spectrometer for coincidence measurements between the Compton scattered photon and the recoil electron are described. Coincidence measurements give direct information on the three-dimensional electron momentum density (EMD) of condensed matter. The present spectrometer measures energy spectra of both the photon and the electron. The energy spectrum of electrons is measured by a time-of-flight method using single-bunch operation at the Photon Factory Accumulator Ring (PF-AR). The energy resolution obtained for the recoil electron is 190 eV, which is better than that of the photon detector, so that a momentum resolution of the three-dimensional EMD of 0.3 atomic units can be achieved.
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Ahuja, Babu Lal, Harsh Malhotra et Sonal Mathur. « Electron Momentum Density In Europium Using A 137Cs Compton Spectrometer ». Zeitschrift für Naturforschung A 60, no 7 (1 juillet 2005) : 512–16. http://dx.doi.org/10.1515/zna-2005-0708.
The isotropic Compton profile of europium, the most reactive lanthanide, has been measured at a resolution of 0.40 a.u. using 661.65 keV gamma-rays. In the absence of a band structure-based Compton profile, the experimental data are compared with renormalised-free-atom (RFA) and free electron models. It is seen that the RFA model with e−-e− correlation agrees better with the experiment than the free electron models. The first derivatives of the Compton profiles show the hybridization effects of s-, p-, d-, f-electrons. From our RFA data we have also computed the cohesive energy of europium. PACS: 13.60.F, 71.15.Nc, 78.70. -g, 78.70.Ck
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Koop, Ivan. « Toroid spectrometer for electron-ion collider ». International Journal of Modern Physics A 35, no 34n35 (18 décembre 2020) : 2044021. http://dx.doi.org/10.1142/s0217751x20440212.
In this paper, we present two options of the toroid magnetic spectrometer dedicated to measure the energy and the polar and the azimuthal angles of the scattered from the ion’s nuclear electrons in the future electron-ion collider DERICA at JINR. These options differ by the opposite sign of the magnetic field. In one of the options, the toroid magnetic field bends electrons towards the collision line, while in the option with the inverted field a bent is done outwards from the beam axis. We show that the last case provides much larger useful fraction of a solid angle for detection of the scattered electrons. The momentum resolution of such a spectrometer is estimated.
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Pang, W. N., et R. C. Shang. « Parallel data acquisition system for electron momentum spectrometer ». Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment 434, no 2-3 (septembre 1999) : 444–48. http://dx.doi.org/10.1016/s0168-9002(99)00502-1.
Weigold, E., YQ Cai, SA Canney, AS Kheifets, IE McCarthy, P. Storer et M. Vos. « Direct Observation of EnergyMomentum Densities in Solids ». Australian Journal of Physics 49, no 2 (1996) : 543. http://dx.doi.org/10.1071/ph960543.
Electron momentum spectroscopy (EMS), based on kinematically complete observations of high energy electron impact ionisation events, directly observes energymomentum dispersion laws and densities of electrons in solids. The valence electronic structure in the near surface region, up to a depth of about 20 Å is probed for thin free-standing films (about 100 Å) by the multiparameter EMS spectrometer at Flinders University. The principles of the measurement are described and its application to the determination of energymomentum densities in a range of amorphous, polycrystalline and crystalline materials is discussed.
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Storer, P., R. S. Caprari, S. A. C. Clark, M. Vos et E. Weigold. « Condensed matter electron momentum spectrometer with parallel detection in energy and momentum ». Review of Scientific Instruments 65, no 7 (juillet 1994) : 2214–26. http://dx.doi.org/10.1063/1.1144730.
Bozzini, J., et Y. Acremann. « Test signal generator for simulating electron events from a momentum microscope ». Journal of Instrumentation 18, no 01 (1 janvier 2023) : P01014. http://dx.doi.org/10.1088/1748-0221/18/01/p01014.
Abstract Preparing experiments that utilize free electron lasers is challenging because obtaining access to the facility is difficult. The integration of detectors into the data acquisition system needs to be tested before the beamtime starts. In this study, we develop a test signal generator that simulates the signals from a delay-line detector used in a time-of-flight electron spectrometer. The output signals of the simulator are connected to the time-to-digital converter electronics and simulate a realistic energy spectrum of a real spectrometer. Through this method, the detector electronics can be tested and integrated into the data acquisition system at the free electron laser before the actual instrument is available on site. In addition, the saturation behavior of the signal processing chain can be tested by changing the number of simulated electrons per pulse.
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Chuan-Gang, Ning, Zhang Shu-Feng, Deng Jing-Kang, Liu Kun, Huang Yan-Ru et Luo Zhi-Hong. « Improvements on the third generation of electron momentum spectrometer ». Chinese Physics B 17, no 5 (mai 2008) : 1729–37. http://dx.doi.org/10.1088/1674-1056/17/5/032.
Thèses sur le sujet "Electron momentum spectrometer":
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Graham, Lisa A. (Lisa Anne) Carleton University Dissertation Chemistry. « Studies in coincidence electron spectroscopy : finite collision volume effects and the characterization of an electron momentum spectrometer ». Ottawa, 1991.
Dennison, John Robert. « (e,2e) spectroscopic investigations of the spectral momentum densities of thin carbon films ». Diss., Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/53869.
An (e,2e) electron scattering spectrometer has been constructed and used for the first time to investigate the spectral momentum density of the valence bands of a solid target. This technique provides fundamental information about the electronic structure of both crystalline and amorphous solids. The three fundamental quantities, the band structure, electron density of states, and electron momentum distribution can be simultaneously derived from the measured (e,2e) cross section.
A review of single electron and (e,2e) scattering theory is given with an emphasis on scattering from solids. The effects of multiple scattering are discussed and a method of deconvoluting those effects from the measured (e,2e) cross section is developed.
There is a detailed description of the spectrometer design and operation with particular attention given to the electron optics and voltage distribution. The algorithms and software for computer aided data acquisition and analysis are also outlined, as is error analysis.
The techniques employed in the preparation and characterization of extremely thin film samples of a-C and single crystal graphite are described.
An analysis of the data taken for a-C samples is given. The data are compared with the results of complementary experiments and theory for graphite, diamond, and a-C which are given in a review of the literature. The existence of a definite dispersion relation ε(q) in amorphous carbon is demonstrated. The a-C band structure appears to be more similar to that of graphite than to that of diamond, however it differs significantly from both in some respects. The measured spectral momentum density seems compatible with a model of a-C based on small, randomly-oriented islands of quasi-2D graphite-like continuous random network structures. However, no definitive interpretations can be made until higher resolution experiments are performed on both a-C and single crystal graphite. Ph. D.
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Kalima, Valence. « Use of magnetic moment invariance in low energy electron spectrometry ». Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61831.
Lermer, Noah. « Development and application of a momentum dispersive multichannel electron momentum spectrometer ». Thesis, 1995. http://hdl.handle.net/2429/8805.
The design, evaluation, and application of a momentum dispersive multichannel
spectrometer for electron momentum spectroscopy (EMS) is reported. The spectrometer
employs a microchannel plate/resistive anode position sensitive detector and a channel electron
multiplier, situated on the exit circle of a cylindrical mirror electron energy analyzer, to
simultaneously measure (e,2e) coincidence events over a ± 30° range of azimuthal angle. A
novel coincidence detection system based on the ‘pile-up’ of pulses from the detectors has
been developed to provide prompt detection of coincidence events. This spectrometer
provides an improvement of one to two orders of magnitude in sensitivity over typical single
channel instruments.
The performance of the new spectrometer has been characterized through measurements
of the binding energy spectra and experimental momentum profiles (XMPs) of the valence
electrons of Ne, Ar, Kr, Xe, CH 4and SiH 4. These measurements show significantly higher
statistical precision than any previously reported EMS work. Consistent with earlier studies,
the present multichannel XMPs exhibit very good agreement with theoretical momentum
profiles calculated using high quality wavefunctions.
The momentum profiles of the helium atom for the transitions to the ground (n=1) and
the excited (n=2, n=3) He⁺ final ion states have been obtained with considerably greater precision than previously reported. The experimental momentum profiles ofH2 and D2 for
transitions to the ground and excited (2pσ[sub u],2sσ-sub g]) ion states have also been measured to high
precision. While the XMPs for the transitions to the ground ion states of each system are
found to be in good agreement with theory, the XMPs for the transitions to the excited ion
states show significant deviations from theoretical profiles calculated with very accurate
correlated wavefunctions. It is suggested that these discrepancies arise from contributions of
higher order collision processes neglected in the plane wave impulse description of the (e,2e)
scattering event normally used in the theoretical interpretation of EMS experiments. While
these additional processes have been discussed with regard to other photon, electron and
proton impact studies of two-electron transitions (i.e. ionization plus excitation, double
ionization), they have not been previously considered in the context of EMS studies.
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Bowles, Cameron Michael Albert. « Pushing the boundaries of condensed matter electron momentum spectroscopy ». Phd thesis, 2008. http://hdl.handle.net/1885/49289.
An electron momentum spectrometer at the Australian National University has been used to study various aspects of different solid state systems. EMS is a transmission mode technique and involves the collision of the incident electron with a bound electron, after which both electrons are ejected and measured in coincidence. Through well defined reaction kinematics the complete valence spectral momentum density A(ɛ,q) can be measured. The spectrometer has been used to measure the spectral momentum densities (spectral functions) of single crystal targets, as well as targets in disordered states. A new spin polarised electron source was constructed and implemented in the ANU spectrometer, which was used to measure spin dependent features of ferromagnetic samples. ¶ ...
Chapitres de livres sur le sujet "Electron momentum spectrometer":
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Krishnan, Kannan M. « Probes : Sources and Their Interactions with Matter ». Dans Principles of Materials Characterization and Metrology, 277–344. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780198830252.003.0005.
Probes are generated using laboratory sources, or in large user facilities. Photon sources include incandescence and plasma discharge lamps. Electron beams are generated using thermionic or field-emission sources. RF plasma sources generate ions that are accelerated and used for scattering experiments. Specimens should be probed first with light, as it causes the least damage. Electron interaction with matter causes beam broadening, atomic displacements, sputtering, or radiolysis leading to mass loss and local contamination. Neutrons are heavier than electrons, penetrate more deeply in materials, and require more sample for analysis. Protons (positive charge, heavier than electrons) go a longer way in the specimen without significant broadening. Ions in solids undergo kinematic collisions with conservation of energy and momentum; they also lose energy continuously as they propagate. In the back-scattering geometry, they form important methods of Rutherford backscattering spectroscopy (RBS) and low-energy ion scattering spectroscopy (LEISS). Medium energy ions generate secondary ions by sputtering that can be analyzed by mass spectrometers to determine specimen composition (SIMS). Alternatively, its composition is analyzed (ICP-MS), by creating an aqueous dispersion and converting it to a plasma. Finally, interaction of high-energy ions with core electrons can lead to inner shell ionization and characteristic X-ray emission (PIXE).
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Fisher, David. « Helium ». Dans Much Ado about (Practically) Nothing. Oxford University Press, 2010. http://dx.doi.org/10.1093/oso/9780195393965.003.0007.
Today we learn at such a young age about the periodic properties of the elements and their atomic structure that it seems as if we grew up with the knowledge, and that everyone must always have known such basic, simple stuff. But till nearly the end of the nineteenth century no one even suspected that such things as the noble gases, with their filled electronic orbits, might exist. Helium was the first one we at Brookhaven looked for in our mass spectrometer, and the first one discovered. This was in 1868, but the discovery was ignored and the discoverer ridiculed. He didn’t care; he had other things on his mind. His name was Pierre Jules César Janssen, and he was a French astronomer who sailed to India that year in order to take advantage of a predicted solar eclipse. With the overwhelming brightness of the sun’s disk blocked by the moon, he hoped to observe the outer layers using the newly discovered technique of absorption spectroscopy. Nobody at the time understood why, but it had been observed that when a bright light shone through a gas, the chemical elements in the gas absorbed the light at specific wavelengths. The resulting dark lines in the emission spectrum of the light were like fingerprints, for it had been found in chemical laboratories that when an element was heated it emitted light at the same wavelengths it would absorb when light from an outside source was shined on it. So the way the technique worked, Janssen reasoned, was that he could measure the wavelengths of the solar absorbed lines and compare them with lines emitted in chemical laboratories where different elements were routinely studied, thus identifying the gases present in the sun. On August 18 of that year the moon moved properly into position, and Janssen’s spectroscope captured the dark absorption lines of the gases surrounding the sun. It was an exciting moment, as for the first time the old riddle could be answered: “Twinkle twinkle, little star, how I wonder what you are.” The answer now was clear: the sun, a typical star, was made overwhelmingly of hydrogen. But to Janssen’s surprise there was one additional and annoying line, with a wavelength of 587.49 nanometers.
Actes de conférences sur le sujet "Electron momentum spectrometer":
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Huang, Y., S. Liu, J. Wang, X. Hu, C. Feng et Q. An. « Development of a high resolution PXI based data acquisition system for electron momentum spectrometer ». Dans 2012 IEEE-NPSS Real Time Conference (RT 2012). IEEE, 2012. http://dx.doi.org/10.1109/rtc.2012.6418154.
ALTAREV, I., K. KIRCH, B. LAUSS, O. NAVILLAT-CUNIC, F. M. PIEGSA, G. PIGNOL, G. QUÉMÉNER et al. « TESTS OF LORENTZ INVARIANCE USING A SPECTROMETER DEDICATED TO THE NEUTRON ELECTRIC DIPOLE MOMENT (nEDM) SEARCH ». Dans Proceedings of the Fifth Meeting. WORLD SCIENTIFIC, 2010. http://dx.doi.org/10.1142/9789814327688_0037.
