H Hyperpolarization of Solutions by Overhauser Dynamic Nuclear Polarization with C-H Polarization Transfer.

Dynamic nuclear polarization (DNP) is a method that can significantly increase the sensitivity of nuclear magnetic resonance. The only effective DNP mechanism for hyperpolarization in solution is Overhauser DNP, which is inefficient for H at high magnetic fields. Here we demonstrate the possibility of generating significant H hyperpolarization in solution at room temperature. To counter the poor direct H Overhauser DNP, we implement steady-state C Overhauser DNP in solutions and then transfer the C hyperpolarization to H via a reverse insensitive nuclei enhanced by polarization transfer scheme. We demonstrate this approach using a 400 MHz gyrotron-equipped 3.2 mm magic angle spinning DNP system to obtain H DNP enhancement factors of 48, 8, and 6 for chloroform, tetrachloroethane, and phenylacetylene, respectively, at room temperature.