NMR Line Narrowing by Means of Rotary Spin Echoes

The dipolar broadened ${\mathrm{F}}^{19}$ resonance line in Teflon has been narrowed by irradiating the solid with strong continuous rf magnetic fields under magic-angle conditions. The transverse magnetization in the rotating frame lost under the action of rf and dc magnetic field inhomogeneities has been recovered by means of rotary spin echoes produced by dc magnetic field pulses. The variation of the longitudinal relaxation with direction and strength of the effective magnetic field in this compound has also been measured.