Emission of electrons

It has been known for many years that strongly heating a metal wire in a vacuum causes emission of electrons from the metal surface. This effect is important for thermionic devices used to control or amplify electrical current, but this aspect of surface emission is not considered here. Rather, the discussion here focuses on the effect of heating a sample substance to a high temperature on a metal wire or ribbon. 

There are two processes where nuclear and atomic contributions are iaterrelated. These are the emission of electrons from the atomic shells as an alternative to the emission of a photon and the emission of bremsstrahlung photons ia the P decay process. 

The complete description of the number of Auger electrons that are detected in the energy distribution of electrons coming from a surface under bombardment by a primary electron beam contains many factors. They can be separated into contributions from four basic processes, the creation of inner shell vacancies in atoms of the sample, the emission of electrons as a result of Auger processes resulting from these inner shell vacancies, the transport of those electrons out of the sample, and the detection and measurement of the energy distribution of the electrons coming from the sample. 

Charging can be a significant problem when the sample is an insulator. Bombarding the sample with positive ions can lead to implantation of positive ions as well as the emission of electrons. One way that this problem can be overcome is by flooding the sample surface with a beam of low-energy electrons [50]. 

A Degarive discharge electrode attracts positive ions and forces them to impact on its surface. These impacts provide an addirional source of electrons which contribute to the process. Ultraviolet light generated by the cormu glow causes photoelectric emission of electrons from the electrode surfaces, which further enhances the formation of free electrons. 

For example, the //V characteristics of devices based on the aluminum chelate complex Alq3, where Ag-Mg or ln-Mg are used as the cathode, can be described by thermionic emission of electrons over the barrier height at the electron injection contact/Alq3 [78]. 

Example H2(g) + Cl2(g) 2 HCl(g). photoelectric effect The emission of electrons from the surface of a metal when electromagnetic radiation strikes it. 

The chemisorbed reaction product can be characterized by more shallow positioning of the energy level with respect to the bottom of conductivity band if contrasted to Z (A ) which results in emission of electron into the conductivity band in compliance with reaction... 

High sensitivity is featured by the electrical methods used to detect EEPs. These are based on measuring small currents that occur in the course of selective ionization of EEPs, or currents of secondary emission of electrons or ions knocked by EEPs out of the surface of solid targets (if such emission is taking place). 

The earlier classical publications in this field belong to Oliphant [120]. In his survey he used a beam of rapid metastable atoms of helium obtained by neutralizing ions on the walls of platinum capillary. Oliphant was the first to observe emission of electrons from a surface of magnesium and molybdenum under the action of metastable atoms, and also rebounding of metastable atoms from a molybdenum surface. 

Emission of electrons from the electrode into the solution with formation of solvated electrons and the subsequent reaction between the solvated electrons and the electron scavenger in solution. 

After several decades of systematic electron spectroscopy in ion-atom collisions by many groups (for recent reviews see Refs. 13 and 51), there are only two data sets of doubly differential experimental cross sections cfa/dE dfl for the emission of electrons with < 1 eV. It has been only recently that, with entirely new and extremely efficient electron spectrometers combined with recoil-ion momentum spectroscopy [52], doubly differential cross sections for ultralow -and low-energy electrons (1.5 meV < < 100 eV) have been obtained by... 

In Figs. 20 and 21 we compare the experimental and CDW-EIS results [38] for 40-keV H+ projectiles incident on H2 and He and for emission of electrons at 0° [doubly differential with respect to the electron polar angle of emission and the energy of the ejected electron d2a/dfldE (10-16 cm2 eV 1 sr 1)]. Both sets of results which did not require normalization are seen to be in very good accord, with the spectra being completely dominated by the ECC cusp. 

Fig. 10. DLTS spectrum for a Schottky-barrier diode on n-type ( 7 x 1015 P/cm3) silicon after hydrogenation (150°C, 50 min). The emission rate window e0 corresponds to delay times of 0.5 and 2.5 ms. Each peak is labeled with the measured activation energy for thermal emission of electrons (Johnson et al., 1987a).

We were first introduced to the photoelectric effect as the emission of electrons when a surface is irradiated with light. The threshold is defined by hv = W where v is the frequency of the light and W a characteristic binding energy for the electron. It was soon realized that... 

Inherently connected to the interaction of ions with a solid is the emission of electrons from the sample. Typical yields are 0.1-0.2 electron per incident argon ion of 2 keV, and 0.2-0.5 at 5 keV [2], For the heavier krypton the values are about equal. Two factors contribute to electron emission ... 

One can compensate for charging by using a so-called flood gun, which sprays low-energy electrons onto the sample. Charging can also be minimized by using a beam of atoms instead of ions as primary particles. In this case, kinetic emission of electrons is the only source of charging, if we ignore the low yields of secondary ions. 

R. E. Honig and J. R. Woolston. Laser-Induced Emission of Electrons, Ions, and Neutral Atoms from Solid Surfaces. Appl. Phys. Lett., 2(1963) 138-139. 

The photoelectric effect is the emission of electrons from the surface of a metal when light shines on it. Electrons are emitted, however, only when the frequency of that light is greater than a certain threshold value characteristic of the particular metal. The alkali metals, with only one electron in their valence shells, have the lowest threshold values. 

All materials emit electrons to an extent dependent on their temperature. Such emission of electrons will cause a body to become positively charged. This effect does not usually become significant until the temperature levels are above the normal incandescent levels, which are to some extent related to this phenomenon. Einbinder (E3) reports that the ionization levels are given by... 

There are two other methods by which particles can become charged. These both involve emission of electrons or ions photoemission and field emission. Photoemission results from the bombardment of the particle surface by electromagnetic radiation. Field emission is the result of subjecting the particle surface to a high electric stress (field intensity). 

From the data of literature it is known that water-soluble derivatives of fullerenes are able to be localized in mitochondria and influence their state as well as enzyme system (Foley et al., 2002). Such intracellular localization of fullerenes C60 could explain biologic effects under irradiation, because generation of free oxygen radicals in the cells occurs during emission of electrons from electron-transport chain of mitochondria. 

Field emission is the emission of electrons from a solid under an intense electric field, usually at ambient temperatures. It occurs by the quantum mechanical tunneling of electrons through a potential barrier (Fig. 13.1). This leads to an exponential dependence of emission current density J on the local electric field, as given by the Fowler Nordheim equation,... 

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