Dynamic Nuclear Spin Polarization of Liquids and Gasesin Contact with Nanostructured Diamond.

Opticalpumping of spin polarization can produce almost completespin order but its application is restricted to select atomic gasesand condensed matter systems. Here, we theoretically investigate anovel route to nuclear spin hyperpolarization in arbitrary fluidsin which target molecules are exposed to polarized paramagnetic centerslocated near the surface of a host material. We find that adsorbednuclear spins relax to positive or negative polarization dependingon the average paramagnetic center depth and nanoscale surface topology.For the particular case of optically pumped nitrogen-vacancy centersin diamond, we calculate strong nuclear spin polarization at moderatemagnetic fields provided the crystal surface is engineered with surfaceroughness in the few-nanometer range. The equilibrium nuclear spintemperature depends only weakly on the correlation time describingthe molecular adsorption dynamics and is robust in the presence ofother, unpolarized paramagnetic centers. These features could be exploitedto polarize flowing liquids or gases, as we illustrate numericallyfor the model case of a fluid brought in contact with an opticallypumped diamond nanostructure. [ABSTRACT FROM AUTHOR]