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.