The retarded interaction between an electron and a spin-0 nucleus is derived from electrodynamical perturbation theory.The contribution of retardation at order v~2/c~2 mimics the Breit interaction [Phys.Rev.34,553(1929);36,388(1930);39,616(1932)]with the Dirac matrix alpha_2 being replaced by p_2/w_2c where p_2 is the linear momentum operator for the nucleus.An effective one-electron retardation operator is obtained in relative coordinates,and this can be used through all orders in perturbation theory without any problem of infinite degeneracy.A few steps of unitary transformation lead to the nonrelativistic limit.The leading terms in retardation corrections to energy are of order(m_2/m_n)alpha~2Z~4(alpha~2m_ec~2).The implications for atomic systems are discussed.
展开▼
