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In physics and chemistry, it is common to measure energy on the atomic scale in the non-SI, but convenient, units electronvolts (eV). 1 eV is equivalent to the kinetic energy acquired by an electron in passing through a potential difference of 1 volt in a vacuum. It is common to use the SI magnitude prefixes (e.g. milli-, mega- etc) with ...
Atomic units are a system of units used in atomic physics, particularly for describing the properties of electrons. The atomic units have been chosen to use several constants relating to the electron: the electron mass , the elementary charge , the Coulomb constant and the reduced Planck constant .
A set of base units in the atomic system as in one proposal are the electron rest mass, the magnitude of the electronic charge, the Planck constant, and the permittivity. [6] [9] In the atomic units system, each of these takes the value 1; the corresponding values in the International System of Units [10]: 132 are given in the table.
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 2). It is common to informally express mass in terms of eV as a unit of mass, effectively using a system of natural units with c set to 1. [3] The kilogram equivalent ...
Atomic units; aulen: atomic unit of length a 0 = 5.291 772 105 44 (82) × 10 −11 m: u r (a 0) = 1.6 × 10 −10 [124] autime: atomic unit of time ħ/E h = 2.418 884 326 5864 (26) × 10 −17 s: u r (ħ/E h) = 1.1 × 10 −12 [125] auvel: atomic unit of velocity a 0 E h /ħ = 2.187 691 262 16 (34) × 10 6 m⋅s −1: u r (a 0 E h ...
In physics, natural unit systems are measurement systems for which selected physical constants have been set to 1 through nondimensionalization of physical units.For example, the speed of light c may be set to 1, and it may then be omitted, equating mass and energy directly E = m rather than using c as a conversion factor in the typical mass–energy equivalence equation E = mc 2.
In some natural unit systems, such as the system of atomic units, e functions as the unit of electric charge. The use of elementary charge as a unit was promoted by George Johnstone Stoney in 1874 for the first system of natural units, called Stoney units. [7] Later, he proposed the name electron for this unit.
The hartree (symbol: E h), also known as the Hartree energy, is the unit of energy in the atomic units system, named after the British physicist Douglas Hartree.Its CODATA recommended value is E h = 4.359 744 722 2060 (48) × 10 −18 J [1] = 27.211 386 245 981 (30) eV.