The electric-dipole moments of an atom II. The contribution from an electric-dipole moment on the electron with particular reference to the hydrogen atom

A quantitative calculation is made of the electric-dipole moment on a free one-electron atom which would result from the existence of a non-zero moment on the electron. It is shown that in the non-relativistic approximation the atomic moment is zero, but that relativistic effects allow a non-zero value. For the ground state of hydrogen the atomic moment is found to be -2 Z 2 α 2 d e , while for the 2s state it is of order d e /α; d e is the electron moment and α is the fine-structure constant. The enhancement in the 2s state is closely connected with the near degeneracy of the 2s and 2p states.