共查询到10条相似文献,搜索用时 93 毫秒
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Greilich A Shabaev A Yakovlev DR Efros AL Yugova IA Reuter D Wieck AD Bayer M 《Science (New York, N.Y.)》2007,317(5846):1896-1899
The hyperfine interaction of an electron with the nuclei is considered as the primary obstacle to coherent control of the electron spin in semiconductor quantum dots. We show, however, that the nuclei in singly charged quantum dots act constructively by focusing the electron spin precession about a magnetic field into well-defined modes synchronized with a laser pulse protocol. In a dot with a synchronized electron, the light-stimulated fluctuations of the hyperfine nuclear field acting on the electron are suppressed. The information about electron spin precession is imprinted in the nuclei and thereby can be stored for tens of minutes in darkness. The frequency focusing drives an electron spin ensemble into dephasing-free subspaces with the potential to realize single frequency precession of the entire ensemble. 相似文献
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The magnetic properties of surfaces are now being explored with electron spectroscopies that use electron spin polarization techniques. The increased activity in surface magnetic measurements with polarized electron beams is spurred by new scientific and technological challenges and is made feasible by recent advances in the technology of sources and detectors of polarized electrons. The ability to grow thin films and to engineer artificial structures permits new phenomena to be investigated at magnetic surfaces and interfaces. For such investigations, spin-polarized electron techniques-such as polarized electron scattering, polarized photoemission, polarized Auger spectroscopy, and scanning electron microscopy with polarization analysis-have been and will probably continue to be used to great advantage. 相似文献
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Modifications of the suprathermal electron population were observed by an electron spectrometer on Spacelab 1 during electron beam injections. The instrument covered its energy range (100 to 12,500 electron volts) and field of view ( approximately 2pi) with high energy, angle, and time resolution. The measurements demonstrate the presence of strong beam-plasma interactions during high-current modes of accelerator operations. Spacecraft charging could be studied as well as processes that accelerated electrons to more than four times the injection energy. 相似文献
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McMorran BJ Agrawal A Anderson IM Herzing AA Lezec HJ McClelland JJ Unguris J 《Science (New York, N.Y.)》2011,331(6014):192-195
Electron beams with helical wavefronts carrying orbital angular momentum are expected to provide new capabilities for electron microscopy and other applications. We used nanofabricated diffraction holograms in an electron microscope to produce multiple electron vortex beams with well-defined topological charge. Beams carrying quantized amounts of orbital angular momentum (up to 100?) per electron were observed. We describe how the electrons can exhibit such orbital motion in free space in the absence of any confining potential or external field, and discuss how these beams can be applied to improved electron microscopy of magnetic and biological specimens. 相似文献
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Drake JF Swisdak M Cattell C Shay MA Rogers BN Zeiler A 《Science (New York, N.Y.)》2003,299(5608):873-877
Three-dimensional particle simulations of magnetic reconnection reveal the development of turbulence driven by intense electron beams that form near the magnetic x-line and separatrices. The turbulence collapses into localized three-dimensional nonlinear structures in which the electron density is depleted. The predicted structure of these electron holes compares favorably with satellite observations at Earth's magnetopause. The birth and death of these electron holes and their associated intense electric fields lead to strong electron scattering and energization, whose understanding is critical to explaining why magnetic explosions in space release energy so quickly and produce such a large number of energetic electrons. 相似文献
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Yang WL Fabbri JD Willey TM Lee JR Dahl JE Carlson RM Schreiner PR Fokin AA Tkachenko BA Fokina NA Meevasana W Mannella N Tanaka K Zhou XJ van Buuren T Kelly MA Hussain Z Melosh NA Shen ZX 《Science (New York, N.Y.)》2007,316(5830):1460-1462
We found monochromatic electron photoemission from large-area self-assembled monolayers of a functionalized diamondoid, [121]tetramantane-6-thiol. Photoelectron spectra of the diamondoid monolayers exhibited a peak at the low-kinetic energy threshold; up to 68% of all emitted electrons were emitted within this single energy peak. The intensity of the emission peak is indicative of diamondoids being negative electron affinity materials. With an energy distribution width of less than 0.5 electron volts, this source of monochromatic electrons may find application in technologies such as electron microscopy, electron beam lithography, and field-emission flat-panel displays. 相似文献
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吕祥辉 《信阳农业高等专科学校学报》2007,17(4):155-156
电子期刊是电子技术、网络技术发展的产物,期刊服务包括电子的和纸质的。网络环境下的期刊服务应摒弃传统的服务理念,变被动服务为主动服务。 相似文献
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Aluminum is considered to approach an "ideal" metal or free electron gas. The valence electrons move freely, as if unaffected by the presence of the metal ions. Therefore, the electron redistribution due to chemical bonding is subtle and has proven extremely difficult to determine. Experimental measurements and ab initio calculations have yielded substantially different results. We applied quantitative convergent-beam electron diffraction to aluminum to provide an experimental determination of the bonding electron distribution. Calculation of the electron distribution based on density functional theory is shown to be in close agreement. Our results yield an accurate quantitative correlation between the anisotropic elastic properties of aluminum and the bonding electron and electrostatic potential distributions. 相似文献