Experiments on the 19F Dipole-Dipole Reservoir in Polytetrafluoroethylene

Abstract

In polytetrafluoroethylene, we have cooled the dipolar reservoir of the fluorine nuclei. In a field of 2.5 Tesla the dipolar relaxation time is approximately 80 s at 3 K and 150 s at 1.8 K. The Zeeman reservoir relaxes in times 50 - 100 times longer. In the material used (a teflon powder produced by Aldrich-Chemie) the Zeeman relaxation time depends on contact to 3He at the surface, contrary to the dipolar relaxation time.