The theory of Sandars and Beck has been tested accurately by calculating, using relativistic Hartree-Fock atomic wave functions, the relativistic quadrupole interaction constants B for the ground states of Mn and ¹⁵¹Eu and the relativistic dipole interaction constant A for the ground state of ¹⁵¹Eu. The results agree in sign and order of magnitude with the experimental values obtained by Sandars and Woodgate and Evans et al.