High field dynamic nuclear polarization at 6.7 T: Carbon-13 polarization above 70% within 20 min

In most applications of dissolution-DNP, the polarization of nuclei with low gyromagnetic ratios such as C-13 is enhanced directly by irradiating the ESR transitions of radicals with narrow ESR lines such as Trityl at low temperatures T = 1.2 K in polarizing fields B-0 <= 5 T. In a field B-0 = 6.7 T at T = 1.2 K, DNP with TEMPO leads to a rapid build-up of proton polarization P(H-1) = 91% with tau(DNP)(1H) = 150 s. CP at low temperatures yields a polarization P(H-1 -> C-13) in excess of 70% within 20 min. After rapid dissolution to room temperature, this is 122000 times larger than the Boltzmann polarization at 300 K and 6.7 T. (c) 2012 Elsevier B.V. All rights reserved.