Contribution of Hydrogen Bonding (HB) to the Leakage Factor in Dynamic Nuclear Polarization (DNP)
One particular application of DNP (1,2) between solvent protons and the electron of a free radical is its use for NMR earth field magnetometers (3), whose sensitivity increases with the DNP Factor (DPF). This factor is proportional to the so-called leakage factor f; f = 1 - T1/T10 where T1, T10, are the nuclear relaxation times of the radical solution and of the pure solvent respectively. More than just leakage phenomena, f expresses the efficiency of the Abragam-Overhauser electron-proton coupling, and then we prefer to call it the “Efficiency Factor”. In this paper, we describe an experimental determination of this factor and its interpretation in terms of DNP, for several M/1000 radical solutions; perdeuterated 2,2,6,6 tetramethyl-4-pipe- ridone 15N-oxide in CH3OH, CH3OD, CD3OH.