35Cl and 19F NMR Spin–Lattice Relaxation Time Measurements and Rotational Diffusion in Liquid ClO3F

The NMR spin–lattice relaxation times of ³⁵Cl and been ¹⁹F have measured by pulse techniques over the entire liquid range of ClO₃F (130–368°K). The chlorine relaxation which is due solely to the nuclear quadrupole interaction can be used together with the known quadrupole coupling constant to determine the correlation time for molecular orientation, ${\tau }_{\text{θ,2}}$ . The fluorine relaxation is dominated by the spin–rotation interaction with only a small intermolecular dipole contribution at the lowest temperatures. In order to obtain the angular momentum correlation time, ${\tau }_J$ , an independent estimate of the spin–rotation tensor was made by combining gas‐phase measurements of $T_1{(}^{19}\mathrm{F})$ with previous data on the chemical shift and gas‐phase dielectric relaxation. The results for this quasispherical molecule are in accord with rotational diffusion theory and Hubbard's relation, ${\tau }_{\text{θ,2}}{\tau }_J\text{\hspace{0.17em}=\hspace{0.17em}I\hspace{0.17em}/\hspace{0.17em}6kT}$ , at the lowest temperatures and agree over the entire range with the extended treatment of McClung.