Magnetic Shielding of 19F in XeF4

The second moment of the ¹⁹F nuclear magnetic resonance of XeF₄ has been measured as a function of temperature and of magnetic field both in the rigid lattice and above a motional transition. A completely general shielding tensor was determined indicating that the previous assumption of axial symmetry about the Xe–F bonds was an oversimplification. The out‐of‐plane component ${\sigma }_x$ was determined uniquely to be 0 ± 8 × 10⁻⁶, referred to the bare ¹⁹F nucleus. Complementary pairs of values for the in‐plane shielding were found to be ${\sigma }_y{\mathrm{(\sigma }}_z{\text{)\hspace{0.17em}=\hspace{0.17em}394\hspace{0.17em}±\hspace{0.17em}25\hspace{0.17em}×\hspace{0.17em}10}}^{\text{−6}}\mathrm{and}{\sigma }_z{\mathrm{(\sigma }}_y{\text{)\hspace{0.17em}=\hspace{0.17em}261\hspace{0.17em}±\hspace{0.17em}25\hspace{0.17em}×\hspace{0.17em}10}}^{\text{−6}}$ . As for XeF₂, the field‐independent rigid‐lattice second moment is larger than that calculated from the average atom positions.