Electron paramagnetic resonance, dynamic polarization and low temperature high field experiments on 3He and fluorocarbon spheres

The authors report the presence of very stable paramagnetic centers, which seem to be peroxy radicals (both mid-chain and end-chain polymer radical). These radicals give an EPR line of around 12 Gauss width at room temperature which broaden to 60 Gauss at helium temperature (EPR at 10 GHz). The concentration is around 1018 centers/cc. When the sample is deoxygenated the T1 of the fluorine is long and allows a dynamic polarization of fluorine with an enhancement factor up to 30 (at 3.8 K). This enhancement factor is also observed on a single layer of 3He, which is the first observance of a dynamic polarization of 3He in dense form