Dynamic Proton Polarization in Butanol Water Below 1 K

Abstract

We have measured the temperature dependence of the dynamic proton polarization in a 0.2-g sample of 95% 1-butanol and 5% water, containing 0.75% of the free radical porphyrexide, between 1.4 and 0.5 K. The largest polarization attained was 67% at 0.5 K. The feasibility of achieving comparable polarization in larger samples and the question of the origin of the observed temperature dependence are discussed.