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 angl e theta from the static magnetic field direction, Their key feature is to detect, during the evolution time t(1), multiquantum transverse co herences whose frequencies are characteristic of the multispin order p roduced by cross-correlation processes, This makes it possible to obta in in-phase magnetization in both dimensions, The three schemes corres pond to the combination of two evolutions due either to static J coupl ing in the transverse plane or to cross-correlation cross-relaxation a long an effective field, This combination allows the conversion of one -spin order into multispin order and the reverse, If only cross-correl ation 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 relax ation rates requires a normalization coefficient which is provided by the simultaneous monitoring of one-spin coherence, These ideas have be en tested experimentally in the case of dipole-dipole cross-correlatio n on a sample of cyclosporin. Buildup curves at various angles theta a re described which yield information on the internal dynamics. (C) 199 7 Academic Press.