Electronvolt
The electronvolt (symbol: eV) is a non-SI unit of energy that has been accepted for use with the SI by the CIPM.[1] It is defined as the kinetic energy gained by an electron on passing through a potential difference of one volt in vacuum:[1] as such, its value in SI units is determined by the measured value of the elementary charge. The 2006 CODATA recommended value is 1 eV = 1.602 176 487(40) × 10−19 J.[2][note 1]
In chemistry, it is often useful to express the electronvolt as a molar quantity, whose value in SI units is determined by the measured value of the Faraday constant. The 2006 CODATA recommended value is 1 eV = 96.485 3399(24) kJ mol−1.[2][note 1]
In particle physics, multiples of the electronvolt are also used as a units of mass based on the principle of mass–energy equivalence. The dimensionally correct unit of mass for use with the SI would be eV/c2, although the division by the square of the speed of light is often assumed and masses quoted simply in megaelectronvolts (MeV, 106 eV) or gigaelectronvolts (GeV, 109 eV). The 2006 CODATA recommended values are 1 GeV/c2 = 1.073 544 188(27) u = 1.782 661 758(44) × 10-27 kg.[2][note 1]
Notes and references
Notes
- ↑ 1.0 1.1 1.2 The values of the fundamental physical constants used for these converstions are (CODATA, 2006):
- Elementary charge: 1.602 176 487(40) × 10−19 C Direct link to value
- Faraday constant: 96 485.3399(24) C mol−1
- Avogadro constant:
- Speed of light:
- Planck constant:
References
- ↑ 1.0 1.1 The International System of Units (SI), 8th ed.; International Bureau of Weights and Measures: Sèvres, France, 2006; pp 125–26. ISBN 92-822-2213-6, <http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf>.
- ↑ 2.0 2.1 2.2 Mohr, Peter J.; Taylor, Barry N.; Newell, David B. CODATA Recommended Values of the Fundamental Physical Constants: 2006. Rev. Mod. Phys. 2008, 80 (2), 633–730. doi:10.1103/RevModPhys.80.633, <http://physics.nist.gov/cuu/Constants/codata.pdf>.
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