We assume that the nucleus is a relativistic point mass with no internal degrees of freedom and derive an expression for its motional contribution to the energies of atomic levels in jj coupling. Our formalism has been implemented in a computer program module sms used in conjunction with the grasp2 multiconfiguration Dirac-Fock package. Representative calculations are presented for some atoms and ions.

• Received 20 May 1992

DOI:https://doi.org/10.1103/PhysRevA.46.3717