Measurement of homonuclear cross-correlation cross-relaxation rates along an effective field: Application to dipole-dipole cross-correlation

We describe three new schemes to explore homonuclear crosscorrelation contributions to relaxation along an effective field tilted by an angle theta from the static magnetic field direction, Their key feature is to detect, during the evolution time t(1), multiquantum transverse coherences whose frequencies are characteristic of the multispin order produced by cross-correlation processes, This makes it possible to obtain in-phase magnetization in both dimensions, The three schemes correspond to the combination of two evolutions due either to static J coupling in the transverse plane or to cross-correlation cross-relaxation along an effective field, This combination allows the conversion of one-spin order into multispin order and the reverse, If only cross-correlation cross-relaxation transfers are involved, there is no restriction on the coupling network. The quantitative exploitation of the results to obtain structural information from cross-correlation-induced relaxation rates requires a normalization coefficient which is provided by the simultaneous monitoring of one-spin coherence, These ideas have been tested experimentally in the case of dipole-dipole cross-correlation on a sample of cyclosporin. Buildup curves at various angles theta are described which yield information on the internal dynamics. (C) 1997 Academic Press.