Editing Atomic units (section)

== Definition ==
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.<ref name="McWeeny1973"/>{{refn|{{citation |author1=Paul Quincey |author2=Peter J Mohr |author3=William D Phillips |title=Angles are inherently neither length ratios nor dimensionless |journal=Metrologia |volume=56 |date=2019 |issue=4 |page=043001 |doi=10.1088/1681-7575/ab27d7 |arxiv=1909.08389 |bibcode=2019Metro..56d3001Q |quote=In [the Hartree system of atomic] units, {{math|''m''<sub>e</sub>}}, {{math|''e''}}, {{math|''ħ''}} and {{math|1/4''πε''<sub>0</sub>}} are all set equal to unity. }} – a reference giving an equivalent set of defining constants.}} In the atomic units system, each of these takes the value 1; the corresponding values in the [[International System of Units]]<ref name="Brochure9_2019">
{{cite web
 |title = 9th edition of the SI Brochure
 |publisher = BIPM
 |date = 2019
 |url = https://www.bipm.org/en/publications/si-brochure/
 |access-date = 2019-05-20
}}</ref>{{rp|132}} are given in the table.

{|class="wikitable"
|+ Base atomic units{{cref|*}}
|-
!scope="col"| Symbol and Name
!scope="col"| Quantity (dimensions){{cref|{{dagger}}}}
!scope="col"| Atomic<br>units{{cref|{{double dagger}}}}
!scope="col"| SI units
|-
| {{tmath|1= \hbar }}, [[reduced Planck constant]] || action (ML<sup>2</sup>T<sup>−1</sup>) || 1  || {{physconst|hbar|ref=no}}&nbsp;<ref>
  {{cite web |title=reduced Planck constant | work={{harvnb|CODATA}}
    |url=http://physics.nist.gov/cgi-bin/cuu/Value?hbar }}</ref>
|-
| {{tmath|1= e }}, [[elementary charge]] || charge (Q) || 1 || {{physconst|e|ref=no}}&nbsp;<ref>
  {{cite web |title=elementary charge | work={{harvnb|CODATA}}
    |url=http://physics.nist.gov/cgi-bin/cuu/Value?e }}</ref>
|-
| {{tmath|1= m_\text{e} }}, [[electron rest mass]] || mass (M) || 1 || {{physconst|me|ref=no}}&nbsp;<ref>
  {{cite web |title=electron mass | work={{harvnb|CODATA}}
    |url=http://physics.nist.gov/cgi-bin/cuu/Value?me }}</ref>
|-
| {{tmath|1= 4 \pi \epsilon_0 }}, [[permittivity]] || permittivity (Q<sup>2</sup>W<sup>−1</sup>L<sup>−1</sup>) ||  1 || {{physconst|auperm|ref=no}}&nbsp;<ref name="auperm">
  {{cite web |title=atomic unit of permittivity |work={{harvnb|CODATA}}
    |url=http://physics.nist.gov/cgi-bin/cuu/Value?auperm }}</ref>
|}

===Table notes===
*{{cnote|*|This arbitrary choice of base units was proposed by McWeeny.}}
*{{cnote|{{dagger}}|See [[Dimensional analysis]]. W represents the dimension of energy, ML<sup>2</sup>T<sup>−2</sup>.<ref name="McWeeny1973"/>}}
*{{cnote|{{double dagger}}|In the 'atomic units' column, the convention that uses dimensionless equivalents has been applied.}}