Araki–Sucher correction

In atomic, molecular and optical physics, the Araki–Sucher correction is a leading-order correction to the energy levels of atoms and molecules due to effects of quantum electrodynamics (QED).^[1] It is named after Huzihiro Araki^[2] and Joseph Sucher,^[3] who first calculated it for the helium atom in 1957. The method is based on a perturbative expansion of the energy in the Bethe–Salpeter equation, and have since been used to calculate corrections for atoms other than helium (e.g. beryllium^[4] and lithium^[5]), and for systems with more than two electrons.^[6][7] The correction typically involves the fine-structure constant ${\displaystyle \alpha }$ and may sometimes include terms of third order and higher (i.e. ${\displaystyle \sim \alpha ^{3}}$).