Atomic displacments in low-temperature electron-irradiated cobalt

Abstract Irradiations of polycrystalline specimens of cobalt at various electron energies and at low temperature were performed. It was found impossible to explain the obtained data by using a simple step function for the probability of displacement P(T) as a function of the kinetic energy T imparted to a struck atom. More involved functions have to be considered. For irradiation temperatures lower than 6 K, the onset threshold is found to be: T d =22 ± 1 eV and the experimental results are best fitted by a theoretical cross-section curve calculated with:P(T)=O if T<22.5 eV =0.50 if 22.5 < T < 31 eV =0.78 if 31 eV < T The onset threshold and the shape of P(T) found are depending on the irradiation temperature. The reasons for this are discussed.