Pressure dependence of NMR data for dilute 3He in solid 4He

In the last four years, groups at Cornell, Sussex and Kharkov have carried out NMR studies of 3He in solid 4He close to the melting curve. Using simple models to interpret the data, values for the 3He-4He quantum tunnelling frequency, J34, of 104-105 sec-1 have been deduced. These values are 2-3 orders of magnitude below J33, the tunnelling frequency for neighbouring particles in pure solid 3He of similar lattice spacing. During this time, three groups of theorists have developed alternative models which lead to values of J34 closer to that expected, i.e. closer to J33. Reported here are new data on the spin diffusion coefficient D and the NMR relaxation times T1 and T2 which give direct experimental evidence that J34 is of the order of J33. (Auth.)