Single crystals were bombarded with 40-500keV Xe ions to doses of between 1011 and 2 x 1016/cm2. Gas release, Rutherford back-scattering, and channelling measurements were used to monitor diffusion. It was found that, at low doses and energies, the gas release was compatible with volume diffusion similar to that of group-I and -VIII elements. The pre-exponential factors were of the order of 10-5cm2/s and the activation energies were much lower than those for self-diffusion or for the diffusion of group-III and V elements. The activation energies for gas diffusion obeyed:

Q(eV) = 0.00105Tm(K)

where Tm was the melting point. It was suggested that gas migration might involve the Turnbull dissociative mechanism. The present data indicated that a fraction of the gas atoms occupied lattice sites. At higher doses, the activation energies for gas diffusion obeyed:

Q(eV) = 0.0021Tm(K)

H.Matzke: Radiation Effects, 1970, 3[1-2], 93-105