Subthreshold events and atomic displacements in electron-irradiated cadmium

Abstract

High-purity zone refined specimens of cadmium were irradiated at liquid helium temperature with electrons in the energy range 0.5–1.7 MeV. From the measurements of the electrical resistivity change rate per incident electron and from an analysis of the recovery spectra up to ∼ 200 °K we deduce that two simultaneous processes are acting under electron bombardment. The first—a subthreshold process—is of a complicated nature and thought to be due to the interaction of the bombarding electrons with very small amounts (∼ 10⁻⁷ per atom) of hydrogen atoms loosely bound to traps, their binding energy being of the order T_s ∼ 10⁻¹ eV. The second is the cadmium atom displacement proper, with an energy threshold of T_d = 19±2 eV.