  The detection of a nuclear spin in an individual molecule represents a key
challenge in physics and biology whose solution has been pursued for many
years. The small magnetic moment of a single nucleus and the unavoidable
environmental noise present the key obstacles for its realization. Here, we
demonstrate theoretically that a single nitrogen-vacancy (NV) center in diamond
can be used to construct a nano-scale single molecule spectrometer that is
capable of detecting the position and spin state of a single nucleus and can
determine the distance and alignment of a nuclear or electron spin pair. The
proposed device will find applications in single molecule spectroscopy in
chemistry and biology, such as in determining protein structure or monitoring
macromolecular motions and can thus provide a tool to help unravelling the
microscopic mechanisms underlying bio-molecular function.
