Generating Unexpected Spin Echoes in Dipolar Solids withπPulses

Dale Li, A. E. Dementyev, Yanqun Dong, R. G. Ramos, S. E. Barrett
2007 Physical Review Letters  
NMR spin echo measurements of C-13 in C60, Y-89 in Y2O3, and Si-29 in silicon are shown to defy conventional expectations when more that one pi pulse is used. Multiple pi-pulse echo trains may either freeze our or accelerate the decay of the signal, depending on the pi-pulse phase. Average Hamiltonian theory, combined with exact quantum calculations, reveals an intrinsic cause for these coherent phenomena: the dipolar coupling has a many-body effect during any real, finite pulse.
doi:10.1103/physrevlett.98.190401 pmid:17677606 fatcat:vjrr2zj2cre4pfoo27id64s5o4