Electronvolt

The electron volt, also electron volt is a unit of energy that is often used in atomic, nuclear and particle physics. Your unit symbol eV.

An electron volts is the amount of energy to which the kinetic energy of an electron is increased as it passes through an acceleration voltage of 1 volt. Its value according to the CODATA recommendation is: ( with a standard deviation of 3.5 × 10-27 J).

The electron volt is not part of the International System of Units ( SI), but is approved for use with the SI and a legal unit.

Designation

The unit is called in German literature predominantly as " electron volts ", ie "volt " with the morpheme " s " between " electron" and. On the other hand, the Regulation Implementing the Law on the units of measurement and the determination of time from December 13, 1985 sees the form of " electron volts " before.

The DIN standard 1301-1 " units - unit name, unit symbol " of October 2010, recommends the form " electron volts ". The standard DIN 66030 "Information technology - Representation of unit names in systems with limited character stock " of May 2002, however, the shape of " electron volts " used.

While the electron volts is a unit of power, the voltage is a unit of the electric voltage.

Use

The electron volt is used in atomic physics and related fields such as experimental elementary particle physics as " handy " unit, see also Natural Units: Both the mass of elementary particles and the energy to which they are brought in particle accelerators, are given in electron volts.

Conversion to the mass is done using the well-known equation from the special theory of relativity

Where is the energy of the mass and the velocity of light. After that corresponds to 1 eV / c ² approximately 1.783 · 10-36 kg.

Handy because to be calculated with the energy of a particle is accelerated in an electric field and is independent of other influences. The direction of movement, the length of the path or of the exact profile of the field strength is not important. The charge of many particles corresponds to an integral multiple of the elementary charge. Instead of using the elementary charge and specify the energy in joules, one can directly specify eV in the unit resulting from an electrical acceleration kinetic energy with them. The conversion of joules in eV occurs approximately in accordance.

Common decimal multiples of electron volts are:

• MeV (milli- electron volts ). For example, a free particle has at room temperature a thermal energy of about 40 meV
• KeV ( kilo-electron volts). For example, a photon of X-ray radiation has about 1-250 keV
• MeV ( mega-electron- volts). Example: the rest energy of an electron is about 0.511 MeV
• GeV ( giga ). Example: the rest energy of a proton is about 0.94 GeV
• TeV ( tera electron volt ). For example, protons in the LHC have a maximum kinetic energy of 4 TeV

The kinetic energy of fast moving heavier atomic nuclei ( heavy ions) are added frequently to per nucleon. The unit is then written AGeV, where A is the mass number. The following applies: Each core with 1 AGeV has the same speed. Similarly, there are, depending on the energy scale of the Atev and AMeV.

As a comparison, the cleavage products of nuclear fission of uranium have a kinetic energy of about 167 MeV together. A typical molecule in the atmosphere has a kinetic energy (thermal energy ) of about 0.03 eV. The photons of visible light (red) have an energy of about 2 eV. The LHC at CERN is scheduled to be protons collide with an energy of 14 TeV and lead nuclei with 1146 TeV. The energy of a single core with about 2 mu.J or 180 mu.J is still very low ( of the nutritional value of a chocolate bar with 2200 kJ corresponds to the 1.1 - trillion - or 12 billion times ). But considering the large number of particles (1.15 × 1011 protons per pulse, in the ring of the LHC there are up to 2808 pulses) followed by a single pulse of 258 kJ already close up to the bar of chocolate. The total energy of the protons present in the ring exceeds this with 724 MJ by far.

Conversion of electron volts in joules per mole

The chemistry is not the energy per particle, but is often expressed per mol ( with the unit J / mol ), which is obtained by multiplying the energy of each particle with the Avogadro constant, for example: wherein the Faraday constant.