3He surface relaxation

Pulsed NMR has been used to study several aspects of 3He surface relaxation. In one experiment, a Carbolac substrate was preplated with N2 and the 3He T1 was measured as a function of the applied field H0. Sharp dips in these T1s occurred when the 3He Larmor frequency matched the nitrogen quadrupole frequency. These features are interpreted as evidence that 3He relaxation pathways involve discrete γhH0 energy exchanges rather than the continuum of energies suggested by models based on impurity scattering. Working with a fluorocarbon substrate, the 3He T1 under conditions of a varying O2, environment were monitored. Though the 19F in the substrate showed acute sensitivity to the O2, the 3He T1 was unaltered in all the trials. This serves as evidence against an O2 role in 3He surface relaxation. The same fluorocarbon substrate was used in a series of experiments which revealed that the 3He and substrate 19F nuclear spin reservoirs were strongly linked. One interesting feature of this link was the easy flow of magnetization between the two spin reservoirs. In addition, the 19F T1 changed by a factor of 10 when a 3He monolayer was absorbed on the surface. This nuclear communication was used to probe several aspects of 3He surface relaxation