Indirect detection of NMR via geometry-dependent dipolar fields, revisited

Journal of Magnetic Resonance
In Press, Accepted Manuscript, Available online 1 March 2007,
Wei Dong and CA. Meriles

We explore the dipolar interactions between two separate nuclear spin ensembles in a mixture containing oil and water. Here we expand initial results (C.A. Meriles and W. Dong, J. Magn. Reson. 181, 331 (2006)) to the case in which both systems have the shape of flat, stacked disks. We find that - spite of the strong inhomogeneity of thecoupling dipolar field - the signal encoded in one of the components can be made approximately proportional to the magnetization in the other. This allows us to use one of these systems as a ‘sensor’ to indirectly reconstruct the resonance spectrum or to determine the relaxation time of the ‘sample’ system. In the regime in which dipolar interactions are sufficiently strong, our method can be set to scale-up weaker signals in a non-linear fashion, which, potentially, could allow one to introduce contrast or to improve detection sensitivity of less magnetized samples.