Measurements were made of 3He spin diffusion and nuclear magnetic resonance relaxation times in sub-monolayers (0.10 layer) of 3He impurities on thin 4He films. Evidence was found for a mobility edge, a marked 4He coverage-dependence of the 3He ground state energy, and the absence of an excited state of 3He at very low 4He coverages. A 1000 to 10000 increase in the diffusion coefficient occurred over a narrow range of 4He coverages (15 to 23/nm2).

P.A.Sheldon, R.B.Hallock: Physical Review Letters, 1996, 77[14], 2973-6