Measurement of Homonuclear Cross-Correlation Cross-Relaxation Rates along an Effective Field: Application to Dipole–Dipole Cross-Correlation

Abstract

We describe three new schemes to explore homonuclear cross-correlation contributions to relaxation along an effective field tilted by an angle θ from the static magnetic field direction. Their key feature is to detect, during the evolution timet1, 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 staticJcoupling 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 θ are described which yield information on the internal dynamics.