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[en] As a result of irradiation of nanoparticles with radius R suspended in liquid water, electrons are formed inside it, diffusing in different directions with the same probability and gradually losing their energy during elastic and inelastic collisions. During the physical and physicochemical stages of the process, some of the electrons are transferred to the surface of the nanoparticle and emit into the water. Using the MATHCAD program, the trajectory of electrons was traced using single-collision, step-by-step and Monte-Carlo methods and the percentage ratio of electrons emitting from the surface of nanoparticles into water was calculated. From the calculations, it was revealed that the emission percentage varies depending on the electron energy and the size of nanoparticles, and all electrons with a mean free path satisfying the λ≥2R condition are emitted from the surface of the nanoparticles into water. Emitting electrons in liquid water lose some of their energy, turning first into thermal electrons, and then solvated.
[en] Advances in electron-source technology may have a large impact on a whole swathe of applications, ranging from flat-panel displays to radar and electric-propulsion systems for spacecraft. Currently most sources boil'' electrons from materials into a vacuum, knock them out using photons or other electrons, or rip them out using high electric fields. But high temperatures and intense fields come at a heavy price for many devices. Now a new method for coaxing electrons from a flat cold cathode has been developed and analysed by Vu Thien Binh of Lyon University and Christophe Adessi of the University of Franche-Comte in France (Phys. Rev. Lett. 2000 85 864; Mat. Res. Soc. Symp. Proc. 2000 621 R4.3.1 at press). The advance could lead to a number of applications with far-reaching effects. (U.K.)
[en] Characteristics of electron emission induced by a surface flashover trigger device in a low-pressure trigger switch were investigated. A test method to measure the emitted charges from the trigger device was developed, and the factors affecting the emitted charges were analyzed. The results indicated that the major emitted charges from the trigger device were induced by surface plasma generated by surface flashover occurring on the trigger dielectric material. The emitted charges and the peak emission current increased linearly with the change in the trigger voltage and bias voltage. The emitted charges collected from the anode were affected by the gap distance. However, the emitted charges were less affected by the anode diameter. Furthermore, the emitted charges and the peak emission current decreased rapidly with the increase in gas pressure in a range from 0 Pa to 100 Pa, and then remained stable or changed slightly when the increase in gas pressure up to 2400 Pa.
[en] Prior to the flashover across an insulator in vacuum, the insulator surface is usually charged. It is of great importance to investigate the charging phenomena for better understanding the flashover characteristics. It is considered that there are two kinds of mechanisms closely related to the surface charging of insulator i.e., the secondary electron emission occurred over an insulator, and while employing a perfect electrode contact ahead of electron emission into vacuum, the charge injection and accumulation occurred inside the surface layer of an insulator. Based on the rigorous analysis of the kinetic processes of both primary and secondary electrons, the related surface charges were theoretically deduced. Involving the detrapping of charges trapped and the recombination of charges injected, the charging process due to charge injection and accumulation was analyzed. Some formulas were given to express the density of surface charges
[en] A brief review is given of experimental investigations of the exoelectron emission accompanying structural transformations in condensed matter. Some possibilities of practical application of this phenomenon are also discussed. (author)
[en] Whenever an incident energetic particle (X ray, gamma or electron) ejects an electron from a deep shell in the electronic cloud, a more external electron goes to this level to fill the hole. The extra energy can be emitted either as X ray (X ray fluorescence) or as an electron called Auger electron. The ratio between these 2 possibilities depends on the charge number of the atom. For atoms lighter than gadolinium the ejection of an Auger electron is more likely. The energy of the Auger electron depends only on the nature of the atom and not on the energy of the incident particle. This feature is the basis of the Auger electron spectroscopy. Lise Meitner observed and described the 'Auger effect' a few month before Pierre Auger did, but it was in the context of an erroneous interpretation of beta spectra. Pierre Auger worked on an improved cloud chamber able to visualized the complete event: first the production of a photoelectron, then the emission of a ray quantum and the absorption of this quantum by the atom followed by the emission of an electron. Auger claimed to have observed up to 3 successive Auger effects in iodine. (A.C.)
[en] Two characterisations of the Cu K β 1,3 spectrum are developed, which are robust and transferable to other experimental x-ray geometries. By observing and considering the significant contribution of radiative Auger emission to the K β profile, we obtain an improved and more robust characterisation. The contribution of the KM 2,3 M 4,5 and KM 2,3 N 1 radiative Auger satellites to the K β 1,3 spectrum is measured to be 1.96%. The contribution of radiative Auger emission is often significant and should be included in defining characteristic x-ray spectra. This is a step in the renewed efforts to resolve inconsistencies in characteristic x-ray spectra between theory and common experimental geometries. The spectrum was measured using a rotating anode, monolithic Si channel-cut double-crystal monochromator and backgammon detector. The experimental setup provides insight into the portability of spectral characterisations of x-ray spectra. (paper)
[en] The initial plasma formation on the surface of a cathode of a vacuum diode, vacuum arc, and many other discharges is highly non-uniform. Micron-sized cathode spots form within nanoseconds. Despite the fundamental importance of cathode spots for the breakdown process, their structure, and the source of the required high energy density were not well understood. When an increasing voltage is applied, enhanced field emission of electrons begins from a growing number of small spots or whiskers. This and the impact of ions stimulate desorption of weakly bound adsorbates from the surface of a whisker. The cross section for ionization of the neutrals has a maximum for ∼ 100 eV electrons. As the diode voltage increases, the 100 V equipotential surface which moves towards the cathode is met by the desorbed neutrals moving away from the cathode. These two regions proceed from no overlap to a significant amount of overlap on a nanosecond time scale. This results in the sharp risetime for the onset of ionization. Ions produced in the ionization region, a few μm from the electron emitting spot are accelerated back. This bombardment with ∼ 100 eV ions leads to surface heating of the spot. Since the ion energy is deposited only within a few atomic layers at a time, the onset of breakdown by this mechanism requires much less current than the joule heating mechanism. Ion surface heating is initially orders of magnitude larger than joule heating. As more ions are produced, a positive space charge layer forms which enhances the electric field and thus strongly enhances the field emitted electron current. The localized build-up of plasma above the electron emitting spot then naturally leads to pressure and electric field distributions which ignite unipolar arcs. The high current density of the unipolar arc and the associated surface heating by ions provide the open-quotes explosiveclose quotes formation of a cathode spot plasma