Spin-orbit effect on the magnetic shielding constant using the ab initio UHF method

A calculational method is proposed for the spin-orbit effect on the magnetic shielding constant using ab initio UHF wave-functions and the finite perturbation method. The method is applied to the 1H and 13C magnetic shielding constants of hydrogen halides and methyl halides, respectively. When the spin-orbit effect is included, the results are in good agreement with experiment, showing the importance of the spin-orbit effect on the chemical shifts of the molecules containing heavier halogen atoms. The dominant contribution is due to the Fermi contact interaction.