High proton spin polarization with DNP using the triplet state of pentacene-d14

The proton spins in a large naphthalene single crystal have been very efficiently polarized using optically excited triplet states of fully deuterated pentacene (C22D14) guest molecules. In a field of 0.3T a proton polarization of 0.50 has been achieved. As technique for dynamic nuclear polarization (DNP) the integrated solid effect (ISE) scheme was employed to transfer the large electron polarization of the triplet states directly to the proton spins on naphthalene.