High-field DNP-induced spin correlated states for magic angle-spinning solid-state NMR experiments

The initial spin states for high-resolution NMR experiments have been expressed as a single spin state, the z-magnetization, as given by the high temperature approximation. Thus, J or dipolar couplings between nuclear spins are prerequisite for preparing spin correlated states, such as multiple quantum states, from the initial single-spin states. Recent high-field dynamic nuclear polarization (DNP) experiments at low temperatures using He gas, however, create hyperpolarized nuclear spin states for magic-angle-spinning solid-state NMR. The high temperature approximation is no longer applicable to such hyperpolarized spin states. These DNP-induced spin states have spin correlated components without the effect of the couplings between nuclear spins. We present NMR experiments for measuring such spin correlated components in the spin state prepared by high-field DNP. We also show its application to the measurement of the absolute proton polarization dependent on nanoscale structures together with our magic-angle-spinning DNP-NMR instrumentation at about 20 K. (author)