1 Electron Volt In Joules

Unit of measurement of energy

In physics, an electronvolt (symbol eV, also written electron-volt and electron volt) is the measure of an corporeality of kinetic energy gained by a single electron accelerating from rest through an electrical potential difference of one volt in vacuum. When used equally a unit of free energy, the numerical value of 1 eV in joules (symbol J) is equivalent to the numerical value of the charge of an electron in coulombs (symbol C). Nether the 2019 redefinition of the SI base of operations units, this sets i eV equal to the verbal value 1.602176 634 ×x^−nineteen J.^[1]

Historically, the electronvolt was devised every bit a standard unit of measure through its usefulness in electrostatic particle accelerator sciences, because a particle with electric charge q gains an free energy E = qV later on passing through a voltage of V. Since q must be an integer multiple of the elementary charge e for whatever isolated particle, the gained energy in units of electronvolts conveniently equals that integer times the voltage.

It is a common unit of energy within physics, widely used in solid state, atomic, nuclear, and particle physics, and loftier-energy astrophysics. It is normally used with SI prefixes milli-, kilo-, mega-, giga-, tera-, peta- or exa- (meV, keV, MeV, GeV, TeV, PeV and EeV respectively). In some older documents, and in the name Bevatron, the symbol BeV is used, which stands for billion (10⁹) electronvolts; it is equivalent to the GeV.

Measurement	Unit	SI value of unit of measurement
Free energy	eV	1.602176 634 ×10^−xix J
Mass	eV/c ²	1.782662 ×10⁻³⁶ kg
Momentum	eV/c	5.344286 ×10⁻²⁸ kg·1000/s
Temperature	eV/k _B	1.160451 812 ×x⁴ Grand
Fourth dimension	ħ/eV	6.582119 ×10^−sixteen south
Altitude	ħc/eV	i.97327 ×10⁻⁷ grand

Definition [edit]

An electronvolt is the amount of kinetic energy gained or lost by a single electron accelerating from rest through an electrical potential difference of 1 volt in vacuum. Hence, information technology has a value of ane volt, 1 J/C, multiplied by the elementary charge e = i.602176 634 ×10^−nineteen C.^[2] Therefore, one electronvolt is equal to one.602176 634 ×10^−nineteen J.^[1]

The electronvolt (eV) is a unit of free energy, but is not an SI unit of measurement. The SI unit of energy is the joule (J).

Mass [edit]

Past mass–free energy equivalence, the electronvolt corresponds to a unit of mass. It is common in particle physics, where units of mass and energy are often interchanged, to express mass in units of eV/c ², where c is the speed of light in vacuum (from E = mc ^two ). It is common to informally express mass in terms of eV every bit a unit of mass, effectively using a organization of natural units with c set to i.^[3] The kilogram equivalent of 1 eV/c ^two is:

1\;{\text{eV}}/c^{2}={\frac {(ane.602\ 176\ 634\times x^{-19}\,{\text{C}})\times 1\,{\text{V}}}{(2.99\ 792\ 458\times 10^{eight}\;\mathrm {m/s} )^{2}}}=1.782\ 661\ 92\times x^{-36}\;{\text{kg}}.

For example, an electron and a positron, each with a mass of 0.511 MeV/c ² , can annihilate to yield 1.022 MeV of energy. A proton has a mass of 0.938 GeV/c ⁱⁱ . In general, the masses of all hadrons are of the order of 1 GeV/c ² , which makes the GeV/c ⁱⁱ a user-friendly unit of mass for particle physics:^[4]

1 GeV/c ² = i.782661 92 ×x⁻²⁷ kg.

The atomic mass abiding (m _u), ane 12th of the mass a carbon-12 atom, is shut to the mass of a proton. To convert to electronvolt mass-equivalent, employ the formula:

m _u = 1 Da = 931.4941 MeV/c ² = 0.9314941 GeV/c ⁱⁱ .

Momentum [edit]

By dividing a particle's kinetic free energy in electronvolts past the primal constant c (the speed of lite), ane can describe the particle'southward momentum in units of eV/c.^[v] In natural units in which the fundamental velocity constant c is numerically ane, the c may informally exist omitted to express momentum as electronvolts.

The free energy momentum relation

Eastward^{ii}=p^{2}c^{two}+m_{0}^{ii}c^{iv}

in natural units (with $c=1$ )

E^{2}=p^{2}+m_{0}^{2}

is a Pythagorean equation. When a relatively high energy is applied to a particle with relatively depression rest mass, it can be approximated as $Eastward\simeq p$ in high-energy physics such that an applied energy in units of eV conveniently results in an approximately equivalent modify of momentum in units of eV/c.

The dimensions of momentum units are T ⁻¹ L M. The dimensions of energy units are T ^−two Fifty ² Chiliad. Dividing the units of energy (such equally eV) past a fundamental abiding (such as the speed of light) that has units of velocity (T ⁻¹ L) facilitates the required conversion for using energy units to describe momentum.

For example, if the momentum p of an electron is said to be 1 GeV, so the conversion to MKS organisation of units can be achieved by:

p=1\;{\text{GeV}}/c={\frac {(one\times 10^{9})\times (one.602\ 176\ 634\times ten^{-19}\;{\text{C}})\times (1\;{\text{Five}})}{2.99\ 792\ 458\times 10^{8}\;{\text{k}}/{\text{south}}}}=v.344\ 286\times 10^{-xix}\;{\text{kg}}{\cdot }{\text{yard}}/{\text{south}}.

Distance [edit]

In particle physics, a system of natural units in which the speed of light in vacuum c and the reduced Planck constant ħ are dimensionless and equal to unity is widely used: c = ħ = 1. In these units, both distances and times are expressed in inverse energy units (while free energy and mass are expressed in the same units, see mass–free energy equivalence). In particular, particle scattering lengths are often presented in units of inverse particle masses.

Exterior this arrangement of units, the conversion factors betwixt electronvolt, second, and nanometer are the following:

\hbar =one.054\ 571\ 817\ 646\times 10^{-34}\ \mathrm {J{\cdot }south} =6.582\ 119\ 569\ 509\times x^{-16}\ \mathrm {eV{\cdot }s} .

The to a higher place relations also allow expressing the mean lifetime τ of an unstable particle (in seconds) in terms of its decay width Γ (in eV) via Γ = ħ/τ . For example, the
B ⁰
meson has a lifetime of 1.530(nine) picoseconds, hateful decay length is cτ = 459.7 μm , or a decay width of (4.302±25)×10⁻⁴ eV.

Conversely, the tiny meson mass differences responsible for meson oscillations are often expressed in the more convenient changed picoseconds.

Energy in electronvolts is sometimes expressed through the wavelength of light with photons of the same energy:

{\frac {1\;{\text{eV}}}{hc}}={\frac {1.602\ 176\ 634\times ten^{-nineteen}\;{\text{J}}}{(2.99\ 792\ 458\times 10^{ten}\;{\text{cm}}/{\text{s}})\times (6.62\ 607\ 015\times 10^{-34}\;{\text{J}}{\cdot }{\text{s}})}}\thickapprox 8065.5439\;{\text{cm}}^{-1}.

Temperature [edit]

In certain fields, such as plasma physics, it is user-friendly to apply the electronvolt to express temperature. The electronvolt is divided by the Boltzmann constant to convert to the Kelvin scale:

{i{\text{ eV}}/k_{\text{B}}}={ane.602\ 176\ 634\times x^{-19}{\text{ J}} \over 1.380\ 649\times 10^{-23}{\text{ J/K}}}=11\ 604.518\ 12{\text{ K}},

where k _B is the Boltzmann abiding.

The k _B is assumed when using the electronvolt to express temperature, for example, a typical magnetic confinement fusion plasma is xv keV (kiloelectronvolt), which is equal to 174 MK (megakelvin).

As an approximation: grand _B T is about 0.025 eV (≈ 290 Thousand / 11604 K/eV ) at a temperature of twenty °C.

Properties [edit]

Energy of photons in the visible spectrum in eV

Graph of wavelength (nm) to free energy (eV)

The free energy Due east, frequency v, and wavelength λ of a photon are related by

E=h\nu ={\frac {hc}{\lambda }}={\frac {4.135\,667\,516\times 10^{-15}\,\mathrm {eV{\cdot }southward} \times 299\,792\,458\,\mathrm {m/south} }{\lambda }}

where h is the Planck constant, c is the speed of light. This reduces to^{[half dozen]}

{\begin{aligned}Eastward\mathrm {(eV)} &=iv.135\,667\,516\times 10^{-xv}\,\mathrm {eV{\cdot }south} \times \nu \\[4pt]&={\frac {1\ 239.841\ 93\,{\text{eV}}{\cdot }{\text{nm}}}{\lambda }}.\end{aligned}}

A photon with a wavelength of 532 nm (green light) would have an free energy of approximately 2.33 eV. Similarly, i eV would represent to an infrared photon of wavelength 1240 nm or frequency 241.8 THz.

Scattering experiments [edit]

In a low-energy nuclear handful experiment, information technology is conventional to refer to the nuclear recoil energy in units of eVr, keVr, etc. This distinguishes the nuclear recoil energy from the "electron equivalent" recoil free energy (eVee, keVee, etc.) measured by scintillation light. For instance, the yield of a phototube is measured in phe/keVee (photoelectrons per keV electron-equivalent free energy). The human relationship betwixt eV, eVr, and eVee depends on the medium the scattering takes place in, and must exist established empirically for each textile.

Energy comparisons [edit]

Energy	Source
5.25×10³² eV	total free energy released from a xx kt nuclear fission device
1.22×ten²⁸ eV	the Planck energy
ten YeV ( 1×10²⁵ eV)	approximate 1000 unification free energy
~624 EeV ( 6.24×10²⁰ eV)	energy consumed by a single 100-watt calorie-free seedling in 1 second ( 100 Westward = 100 J/south ≈ 6.24×10²⁰ eV/due south)
300 EeV ( iii×10²⁰ eV = ~ 50 J)	The first ultra-high-energy cosmic ray particle observed, the so-chosen Oh-My-God particle.^[10]
ii PeV	ii petaelectronvolts, the highest-energy neutrino detected past the IceCube neutrino telescope in Antarctica^[xi]
xiv TeV	designed proton center-of-mass standoff energy at the Large Hadron Collider (operated at 3.5 TeV since its start on 30 March 2010, reached thirteen TeV in May 2015)
1 TeV	a trillion electronvolts, or i.602×10⁻⁷ J, about the kinetic energy of a flight mosquito^[12]
172 GeV	rest energy of top quark, the heaviest measured elementary particle
125.one±0.two GeV	free energy corresponding to the mass of the Higgs boson, as measured by two separate detectors at the LHC to a certainty amend than five sigma^[xiii]
210 MeV	average energy released in fission of one Pu-239 atom
200 MeV	approximate average energy released in nuclear fission fission fragments of i U-235 atom.
105.vii MeV	remainder energy of a muon
17.half dozen MeV	average free energy released in the nuclear fusion of deuterium and tritium to class He-4; this is 0.41 PJ per kilogram of product produced
2 MeV	judge average energy released in a nuclear fission neutron released from one U-235 atom.
i.ix MeV	residual energy of upward quark, the lowest mass quark.
one MeV ( 1.602×10⁻¹³ J)	near twice the residuum energy of an electron
1 to 10 keV	judge thermal temperature, $k_{\text{B}}T$ , in nuclear fusion systems, like the core of the sunday, magnetically confined plasma, inertial solitude and nuclear weapons
13.6 eV	the energy required to ionize diminutive hydrogen; molecular bond energies are on the order of 1 eV to ten eV per bond
one.6 eV to 3.iv eV	the photon free energy of visible light
1.i eV	energy $E_{g}$ required to break a covalent bond in silicon
720 meV	free energy $E_{g}$ required to interruption a covalent bond in germanium
< 120 meV	approximate rest energy of neutrinos (sum of 3 flavors)^[fourteen]
25 meV	thermal free energy, $k_{\text{B}}T$ , at room temperature; ane air molecule has an average kinetic energy 38 meV
230 μeV	thermal energy, $k_{\text{B}}T$ , of the catholic microwave groundwork

Per mole [edit]

I mole of particles given i eV of free energy each has approximately 96.5 kJ of energy – this corresponds to the Faraday abiding (F ≈ 96485 C⋅mol^−one ), where the energy in joules of n moles of particles each with energy E eV is equal to E·F·n.

Run into too [edit]

Orders of magnitude (energy)

References [edit]

^ ^a ^b "2018 CODATA Value: electron volt". The NIST Reference on Constants, Units, and Dubiety. NIST. 20 May 2019. Retrieved 2019-05-20 .
^ "2018 CODATA Value: elementary accuse". The NIST Reference on Constants, Units, and Uncertainty. NIST. 20 May 2019. Retrieved 2019-05-20 .
^ Barrow, J. D. (1983). "Natural Units Earlier Planck". Quarterly Journal of the Majestic Astronomical Society. 24: 24. Bibcode:1983QJRAS..24...24B.
^ Gron Tudor Jones. "Free energy and momentum units in particle physics" (PDF). Indico.cern.ch . Retrieved v June 2022.
^ "Units in particle physics". Associate Teacher Institute Toolkit. Fermilab. 22 March 2002. Archived from the original on xiv May 2011. Retrieved 13 February 2011.
^ "CODATA Value: Planck constant in eV s". Archived from the original on 22 January 2015. Retrieved 30 March 2015.
^ What is Light? Archived December 5, 2013, at the Wayback Auto – UC Davis lecture slides
^ Elert, Glenn. "Electromagnetic Spectrum, The Physics Hypertextbook". hypertextbook.com. Archived from the original on 2016-07-29. Retrieved 2016-07-30 .
^ "Definition of frequency bands on". Vlf.information technology. Archived from the original on 2010-04-30. Retrieved 2010-ten-16 .
^ Open Questions in Physics. Archived 2014-08-08 at the Wayback Machine German language Electron-Synchrotron. A Research Eye of the Helmholtz Association. Updated March 2006 by JCB. Original by John Baez.
^ "A growing astrophysical neutrino signal in IceCube now features a 2-PeV neutrino". Archived from the original on 2015-03-19.
^ Glossary Archived 2014-09-15 at the Wayback Car - CMS Collaboration, CERN
^ ATLAS; CMS (26 March 2015). "Combined Measurement of the Higgs Boson Mass in pp Collisions at √southward=7 and viii TeV with the ATLAS and CMS Experiments". Concrete Review Letters. 114 (xix): 191803. arXiv:1503.07589. Bibcode:2015PhRvL.114s1803A. doi:10.1103/PhysRevLett.114.191803. PMID 26024162.
^ Mertens, Susanne (2016). "Direct neutrino mass experiments". Journal of Physics: Conference Series. 718 (2): 022013. arXiv:1605.01579. Bibcode:2016JPhCS.718b2013M. doi:x.1088/1742-6596/718/2/022013. S2CID 56355240.

External links [edit]

BIPM's definition of the electronvolt
physical constants reference; CODATA data