Atomic units

Atomic units (au) form a system of units convenient for atomic physics, electromagnetism, and quantum electrodynamics, especially when the focus is on the properties of electrons. There are two different kinds of atomic units, which one might name Hartree atomic units and Rydberg atomic units, which differ in the choice of the unit of mass and charge. This article deals with Hartree atomic units. In au, the numerical values of the following six physical constants are all unity by definition:Two properties of the electron, its mass and charge;Two properties of the hydrogen atom, its Bohr radius and the absolute value of its electric potential energy in the ground state;Two constants, Dirac's and that for Coulomb's Law.
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