Rotational resonance echoes in the nuclear magnetic resonance of spinning solids

A procedure is described which leads to the reversal of the rotor driven evolution of nuclear spins at rotational resonance, inducing the formation of a new class of spin echoes. The echoes are produced by radio-frequency pulse sequences which suspend the evolution of the nuclear spin states for a finite fraction of a sample rotation period. Experimental demonstrations are given. The echoes may be exploited to extract scalar J-couplings and to investigate the relaxation behavior of coupled spins in a rotating powdered solid.