Pulsed NMR of monolayer and near-monolayer films of 3He adsorbed on Grafoil at low temperatures

Pulsed NMR measurements at 30 MHz of near-monolayer coverages of ³He on Grafoil have been made between 4.2 and 0.1 K. The time constants of the free induction decay indicate that below 4.2 K the mobility of ³He in an exact monolayer is smaller than that at lower coverages or at coverages above one monolayer, in agreement with the results found by Hegde and Daunt, by Cowan and co-workers, and by Rollefson. Furthermore, in spite of rf heating of the sample, we were able to conclude that the mobility of ³He in nearmonolayers films decreases as the temperature is decreased below 4.2 K. At 4K and 30MHz our measurements give T₁ = 1 ± 0.3 sec for coverages between 0.6 and 1.35 monolayers. This is in agreement with previous work.Supported by the National Science Foundation.