Dissolution dynamic nuclear polarization of deuterated molecules enhanced by cross-polarization

We present novel means to hyperpolarize deuterium nuclei in ¹³CD₂ groups at cryogenic temperatures. The method is based on cross-polarization from ¹H to ¹³C and does not require any radio-frequency fields applied to the deuterium nuclei. After rapid dissolution, a new class of long-lived spin states can be detected indirectly by ¹³C NMR in solution. These long-lived states result from a sextet-triplet imbalance (STI) that involves the two equivalent deuterons with spin I = 1. An STI has similar properties as a triplet-singlet imbalance that can occur in systems with two equivalent I = 12 spins. Although the lifetimes T_STI are shorter than T₁(C_z), they can exceed the life-time T₁(D_z) of deuterium Zeeman magnetization by a factor of more than 20.