Relativistic theory of the magnetic shielding constant:. a Dirac-Fock finite perturbation study

Four-component relativistic theory of the magnetic shielding constant is presented, based on the matrix Dirac-Fock finite perturbation method and implemented for numerical calculations with the MOLFDIR program. In contrast to the non-relativistic and quasi-relativistic formalisms, the shielding constant is written as a single term. Our formulation avoids explicit use of the positron states, in contrast to the conventional sum-over-states formalism. The magnetic shielding constants of the noble gas atoms, He through Xe, and those of H ₂, HF and HCl are calculated and compared with values obtained in non-relativistic calculations.