Direct enhancement of any solution NMR signal using the distant dipolar fields created by highly polarized and concentrated nuclear spin systems

Abstract

Peculiar nuclear spin systems can be polarized at a level of thousands times the value obtained at thermal equilibrium, for instance by optical pumping. When concentrated, these systems create a sizeable average dipolar field which is experienced by any nuclear spin. We propose to use these distant dipolar fields for performing a polarization transfer in the Hartmann-Hahn conditions. We report the maximum enhancement value calculated using the spin temperature approach and first theoretical insights on the polarization transfer rate. Using, as an example, dissolved laser-polarized xenon, we show that by spin-locking both xenon spins and a proton spin of a solute, the polarization of the latter is enhanced. This is obtained without the existence of chemical interaction between the two entities and with characteristic rising time not directly correlated to the proton self-relaxation time. By its generality and its non-local feature, this approach could make possible nuclear magnetic resonance spectroscopy on very dilute systems.