Electron An elementary particle

Electron An elementary particle with a unit negative electric charge and a mass of 1/1,837 that of a proton. Electrons surround the positively charged nucleus of an atom and determine the chemical properties of the atom. 

Electron - An elementary particle in the family of leptons, with negative charge and spin of 1/2. 

As far as is known, ordinary matter is made of tiny building blocks called elementary particles. For example, an atom is made up of a nucleus surrounded by one or more electrons. As far as scientists have been able to determine, the electrons are elementary particles, not made of anything simpler. Fdowever, an atomic nucleus is not clcmcntai y, but is a composite particle made up of simpler particles called protons and neutrons. (The lightest nucleus is the nucleus of ordinai y hydrogen, which consists of only a single proton.) Today, physicists believe that even protons and neutrons are not elementai y but are composite particles made up of still simpler building blocks called quarks. 

Every type of particle has a specific unique value of s, which is called the spin of that particle. The particle may be elementary, such as an electron, or composite but behaving as an elementary particle, such as an atomic nucleus. All He nuclei, for example, have spin 0 all electrons, protons, and neutrons... 

On the other hand, the permanent EDM of an elementary particle vanishes when the discrete symmetries of space inversion (P) and time reversal (T) are both violated. This naturally makes the EDM small in fundamental particles of ordinary matter. For instance, in the standard model (SM) of elementary particle physics, the expected value of the electron EDM de is less than 10 38 e.cm [7] (which is effectively zero), where e is the charge of the electron. Some popular extensions of the SM, on the other hand, predict the value of the electron EDM in the range 10 26-10-28 e.cm. (see Ref. 8 for further details). The search for a nonzero electron EDM is therefore a search for physics beyond the SM and particularly it is a search for T violation. This is, at present, an important and active held of research because the prospects of discovering new physics seems possible. 

Beta particle (symbol 3) An elementary particle emitted from a nucleus during radioactive decay, with a single electrical charge and mass equal to 1/1,837 that of a proton. A negatively charged beta particle is identical to an electron. A positively charged beta particle is called a positron. Beta radiation can cause burns, and beta emitters are... 

Proton An elementary particle with a single positive electrical charge and a mass approximately 1,837 times that of an electron the nucleus of the ordinary, or light hydrogen, atom. Protons are constituents of all... 

ELECTRON. Discovered by J. J. Thompson in 1896, the electron is an elementary particle of rest mass... 

The results concerning the allowance for the / -source molecular structure (Kaplan et al., 1982,1983) were used in reduction of the new experimental data obtained by the ITEP group. Table I (Boris et al., 1983) shows the most probable values of the neutrino rest mass obtained by data reduction using the models of a bare nucleus, of a tritium atom, and of a real valine molecule. The reduction of the new experimental data within the bare-nucleus model did not lead to a nonzero rest mass of the neutrino. The allowance for the electron structure of valine gives mvc2 = 33 eV.2 Thus, the quantum chemical calculations proved to be a necessary step in the reduction of the data concerning the properties of an elementary particle. 

To appreciate this time-lag, it is useful to recall that the electron was not recognized as an elementary particle until the twentieth century. Electron beams had been known as cathode rays since 1876, but their corpuscular nature was recognized only in 1897 [12]. The term electron was introduced in 1891 to designate the fundamental unit of electricity, namely the electric charge of a hydrogen ion [13]. Only later was it applied to Thompson s corpuscules, and it achieved general acceptance with Millikan s quite accurate determination of the electronic charge by the oil drop method [14,15]. 

Photonics is playing an ever-increasing role in our modern information society. Photon is gradually replacing the electron, the elementary particle in electronics. Several hooks and reviews have appeared dealing with the theory of nonlinear optics and the structural characteristics and applications of nonlinear optical molecules and materials [1—18]. Tlie earliest nonlinear optical (NLO) effect discovered was the electro-optic (EO) effect. The linear EO coefficient defines the Pockel effect, discovered in 1906, while the quadratic (nonlinear) EO coefficient s,i relates to the Kerr effect, discovered 31 years later (1875). Truly, all-optical NLO effects were not discovered until the discovery of lasers. Second harmonic generation (SHG) was first observed in a single crystal of quartz by Franken et al. [1] in 1961. They frequency doubled the output of a ruby laser (694.3 nm) into the 383... 

The three orbital quantum numbers n, /, and m appear naturally when the Schrodinger equation is solved, There is also a spin quantum number, s, the value of which can be visualized as related to the spin of the electron on its own axis. This quantum number does not appear when the wave equation is solved, but certain quantum-mechanical treatments lead to the conclusion that an elementary particle such as an electron can have two spin angular momentum values, which are specified by the spin quantum numbers -j-4 and —4. We can conveniently think of these two quantum... 

The g-factor of an elementary particle is introduced as a ratio of its magnetic moment jx to its spin angular momentum s, expressed in units of (q/2m). For the electron, in terms of the Dirac theory... 

The quantum levels of nuclei are characterized by several quantum numbers, an important one being the nuclear spin. The spin value for the Cs ground state level is 7/2, while that of " Ba is 11/2. The electron emitted is an elementary particle of spin 1/2. In nuclear reactions the nuclear angular momentum must be conserved (4.8), which means that in radioactive decay processes the difference in total spin between reactant and products must be an integral value (4.10). Inspection of our example shows that this conservation of spin rule is violated if the reaction is complete as we have written it. The sum of the spin of the " Ba and of the electron is 11/2 + 1/2 or 6, while that of the Cs is 7/2. Therefore, the change in spin (AT) in the process would seem to be 5/2 spin units. Inasmuch as this is... 

In 1931, when a British physicist, Paul Dirac, was developing quantum mechanics,bis equations showed the probable existence of an elementary particle, called a positron, having the same mass as an electron but with a positive rather than a negative charge. The existence of positrons was subsequently proven, when they were detected in cosmic radiation by Nobel Prize winner, Carl Anderson. 

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