1H Polarization above 60% at room temperature by triplet dynamic nuclear polarization
1H polarization of 61% was achieved by Dynamic Nuclear Polarization using photoexcited triplet electrons (Triplet-DNP) at room temperature and in 0.64 T. We introduced dibenz[a, h]anthracene as a new host molecule of the polarizing agent, pentacene-d14. Its rigid structure provides a long spin-lattice relaxation time (T1) of more than 2 hours at room temperature. The single crystal of dibenz[a, h]anthracene doped with 0.05 mol% pentacene-d14 was grown by the Bridgman method, and cut into a small piece of ~1 mg for Triplet-DNP experiment. The 1H polarization buildup and relaxation measurements indicated that paramagnetic relaxation became the major source of the relaxation than spin-lattice relaxation. Finally, two promising applications of room-temperature hyperpolarization, i .e. nuclear ordering and radiation-tolerant polarized target, are discussed.