Vibrational Corrections to the Nuclear-Magnetic Shielding and Spin–Rotation Constants for Hydrogen Fluoride. Shielding Scale for 19F

The theory of vibrational effects on the nuclear shielding and spin–rotation constants for a diatomic molecule is outlined. Corrections for these effects are calculated theoretically for both ¹H and ¹⁹F nuclei in the HF molecule. The theoretically calculated isotopic shift for ¹⁹F shielding between DF and HF is in good agreement with the zero pressure experimental value, 2.5 ± 0.5 ppm. The shielding for the vibrating molecule at 300°K is computed from the theoretically calculated value for ${\sigma }_F^d$ and the experimentally measured spin–rotation constant, as ${\mathrm{〈\sigma }}_F\text{(HF)〉\hspace{0.17em}=\hspace{0.17em}410\hspace{0.17em}±\hspace{0.17em}6}\mathrm{ppm}$ . The measured chemical shift between the HF monomer and SiF₄(gas) then provides a practical ¹⁹F reference of known shielding, ${〈}_F({\mathrm{SiF}}_4\text{)〉\hspace{0.17em}=\hspace{0.17em}363\hspace{0.17em}±\hspace{0.17em}6}\mathrm{ppm}$ . Vibrational corrections are applied to the measured proton shielding in HF gas at zero pressure to obtain the shielding constant as ${\sigma }_H(\mathrm{HF}\text{)\hspace{0.17em}=\hspace{0.17em}29.2\hspace{0.17em}±\hspace{0.17em}0.5}$ ppm for the nonvibrating molecule at the equilibrium internuclear distance. Combination of this with the measured spin–rotation constant leads to a separate determination of experimental values for ${\sigma }_H^d$ and ${\sigma }_H^p$ , with arbitrary choice of gauge origin, for the non‐vibrating molecule.