Communication: The absolute shielding scales of oxygen and sulfur revisited

We present an updated semi-experimental absolute shielding scale for the ¹⁷O and ³³S nuclei. These new shielding scales are based on accurate rotational microwave data for the spin–rotation constants of H₂¹⁷O [Puzzarini et al., J. Chem. Phys. 131, 234304 (2009)], C¹⁷O [Cazzoli et al., Phys. Chem. Chem. Phys. 4, 3575 (2002)], and H₂³³S [Helgaker et al., J. Chem. Phys. 139, 244308 (2013)] corrected both for vibrational and temperature effects estimated at the CCSD(T) level of theory as well as for the relativistic corrections to the relation between the spin–rotation constant and the absolute shielding constant. Our best estimate for the oxygen shielding constants of H₂¹⁷O is 328.4(3) ppm and for C¹⁷O −59.05(59) ppm. The relativistic correction for the sulfur shielding of H₂³³S amounts to 3.3%, and the new sulfur shielding constant for this molecule is 742.9(4.6) ppm