Is the speed of an electron constant




The electron [ˈEːlɛktrɔn, eˈlɛk-, elɛkˈtroːn] (from agr. Ἤλεκτρονelectron, "Amber", on which electricity was first observed; Coined by George Johnstone Stoney in 1891) is a negatively charged elementary particle. Its symbol is e⁻.

In the experiments that have been possible up to now, electrons show no internal structure and can therefore be assumed to be point-shaped. The experimental upper limit for the size of the electron is currently around 10−19 m.

In atoms and ions, electrons form the electron shell. Each of the bound electrons can be clearly identified by four quantum numbers (n, l, m and s) (see also Pauli principle). The free mobility of some of the electrons in metals is the cause of the electrical conductivity of metallic conductors.

The experimental proof of electrons was first achieved in 1897 by the British Joseph John Thomson.

During the beta decay of an atomic nucleus, an electron is generated and emitted (regardless of the atomic shell).

properties

An electron is a "quantum object", which means that the position and momentum uncertainty described by Heisenberg's uncertainty principle is in the measurable range, so that, similar to light, both wave and particle properties can be observed. In an atom, the electron can be viewed as a standing wave of matter.

The electron is the lightest electrically charged elementary particle. Because of the conservation of charge and energy, electrons must therefore be stable. Indeed, so far there is no experimental evidence of electron decay; According to the experimental data, the lifetime of the electron must be greater than 1024 Be years.

Electrons belong to the group of leptons and, like all leptons, have a spin of ½. As particles with half-integer spin, they belong to the class of fermions and are therefore particularly subject to the Pauli principle.

Their antiparticles are the positrons, symbol e+with which they agree in all properties except for their electrical charge.

Electrons that have detached from their atoms in polar solvents such as water or alcohols are known as solvated electrons. When alkali metals are dissolved in ammonia, they are responsible for the strong blue color.

Some of the basic properties of the electron, listed in the table on the right, are linked by the magnetic moment of the electron spin: . It is the magnetic moment of the electron spin, me the rest mass of the electron, e his charge and the spin. Gs is called the Landé or g factor. The term before , which describes the ratio of the magnetic moment to the spin, is called the gyromagnetic ratio of the electron. According to the Dirac theory (relativistic quantum mechanics), for the electron is the theoretical value of Gs exactly equal to 2. However, effects of quantum electrodynamics cause a (slight) deviation in the value for Gs of 2. The resulting deviation of the magnetic moment is called anomalous magnetic moment of the electron designated.

In the cathode ray tube or Braun tube, electrons emerge from a heated hot cathode and are accelerated in the vacuum by an electric field in the direction of the field (towards the positive anode). Magnetic fields deflect the electrons perpendicular to the direction of the field and perpendicular to the current direction of flight (Lorentz force). It was these properties of the electrons that made the development of the television and computer monitor and their use in technological applications (electron gun) possible.

The mass of an electron at rest is constant. In the case of moving electrons (and an electron is always in motion under normal conditions), the increase in mass must be taken into account according to the theory of relativity. This increase in mass can be easily observed in electrons, as they can easily be accelerated to high speeds due to their charge and low mass. The mass can then be determined by deflection in a magnetic field. The increase in the mass of an electron was first demonstrated by Walter Kaufmann in 1901.

In a solid, the electron experiences interactions with the crystal lattice. Its behavior can then be described by using the deviating effective mass instead of the electron mass, which is also dependent on the direction of movement of the electron.

A distinction must be made between the size of the electron and its cross-section for interaction processes. When X-rays are scattered by electrons, an effective cross-section is obtained that has an effective electron radius of about 3 · 10−15 m would correspond to. The same order of magnitude would result from a classical (not quantum-theoretical) description of the electron under the assumptions:

  1. The electron is spherical, it represents a spherical capacitor
  2. The charge is evenly distributed on the surface
  3. The potential energy of the charge corresponds to the rest energy mec2.

The total scattering cross-section of photons to electrons is 8/3 π in the limiting case of small photon energiesre2, in which re is the classical electron radius (see Thomson scattering and Compton scattering).

See also:Stern-Gerlach experiment

Category: elementary particles