Eh) a unit of energy used in atomic and moleclar physics, equal to about 4.3598 x 10-18 joule or 27.212 electron volts. The unit is named for the British physicist and mathematician Douglas R. Hartree (1897-1958).

( Eh) Compare with atomic unit. The atomic unit of energy, equal to 4.359 743 81 × 10-18 J ± 0.000 000 34 × 10-18 J [ 1998 CODATA values].

One atomic unit of energy, equal to 2625.5 kJ/mol, 627.5 kcal/mol, 27.211 eV, and 219474.6 cm-1.