19F Rotating Frame Nuclear Magnetic Relaxation in Liquid CHFCl2 and CFCl3

By a suitable choice of the forced precession frequency ω₁, the rotating frame nuclear magnetic relaxation rate $T_{\text{1p}}^{\text{−1}}$ of ¹⁹F in liquid CHFCl₂ and CFCl₃ at room temperature can be dominated by the effect of the scalar coupling of ¹⁹F with ³⁵Cl and ³⁷Cl. From the measured variation of T_1ρ with ω₁, the isotropic scalar coupling constants were determined with the following results: $J_{{}^{19}{\mathrm{F}}^{35}\mathrm{Cl}}\text{= 27.6 ± 0.5}\mathrm{Hz}$ , $J_{{}^{19}{\mathrm{F}}^{37}\mathrm{Cl}}\text{= 23.0 ± 0.5}\mathrm{Hz}$ in CHFCl₂; $J_{{}^{19}{\mathrm{F}}^{35}\mathrm{Cl}}\text{= 13.7 ± 0.5}\mathrm{Hz}$ , $J_{{}^{19}{\mathrm{F}}^{37}\mathrm{Cl}}\text{= 11.4 ± 0.5}\mathrm{Hz}$ in CFCl₃.