Polarization measurements of TEMPO-doped butanol targets

Dynamic nuclear polarization (DNP) measurements have been performed in butanol and deuterated butanol. Both target materials have been chemically prepared for the DNP process with the highly stable free nitroxyl radical 2,2,6,6-tetramethyl-piperidine-1-oxyl, also known as TEMPO. Maximum proton polarization values of 89.2% and maximum deuteron polarization values of 38.4% have been obtained in a magnetic field of 2.5 T and at a temperature of about 200 mK. Polarization relaxation times of >200 h (protons) and >100 h (deuterons) have been measured at 0.35 T and 60 mK. The results together with an easy preparation procedure make TEMPO-doped butanol attractive for the frozen spin operation mode of polarized solid-state targets.