The hartree (symbol: E_''h or Ha), also known as the Hartree energy, is the atomic unit of energy, named after the British physicist Douglas Hartree. It is defined as 2R₈hc, where R₈ is the Rydberg constant, h is the Planck constant and c is the speed of light. The 2010 CODATA recommended value is E_h = = . The 2006 CODATA recommended value was E_h = = .

The hartree (symbol: E_''h or Ha), also known as the Hartree energy, is the atomic unit of energy, named after the British physicist Douglas Hartree. It is defined as 2R₈hc, where R₈ is the Rydberg constant, h is the Planck constant and c is the speed of light. The 2010 CODATA recommended value is E_h = = . The 2006 CODATA recommended value was E_h = = .