MULTIPLE NONLINEAR STIMULATED ECHOES

Three-pulse sequences in the presence of magnetic field gradients at h igh magnetic fields produce multiple nonlinear stimulated echoes (NOSE ) at times n tau(1) after the third pulse, where n is an integer and t au(1) the interval between the first two pulses, These phenomena are d ue to the demagnetizing field produced by the spatial modulation of th e nuclear magnetization arising in the sample after the first two puls es, The theory is presented and compared with experiments. The depende nce of the NOSE amplitudes on the flip angles and on the pulse interva ls is described, Implications for multidimensional NMR experiments bas ed on sequences of three or more pulses in the presence of field gradi ents are discussed. (C) 1997 Academic Press.