  We report on experiments that quantify the role of a central electronic spin
as a relaxation source for nuclear spins in its nanoscale environment. Our
strategy exploits hyperpolarization injection from the electron as a means to
controllably probe an increasing number of nuclear spins in the bath, and
subsequently interrogate them with high fidelity. Our experiments are focused
on a model system of a nitrogen vacancy (NV) center electronic spin surrounded
by several hundred 13C nuclear spins. We observe that the 13C transverse spin
relaxation times vary significantly with the extent of hyperpolarization
injection, allowing the ability to measure the influence of electron mediated
relaxation extending over several nanometers. These results suggest interesting
new means to spatially discriminate nuclear spins in a nanoscale environment,
and have direct relevance to dynamic nuclear polarization and quantum sensors
and memories constructed from hyperpolarized nuclei.
