Superconductivity in Irradiated Palladium

Pure palladium films, evaporated between 4.2 and 300 K, can be transformed into superconductors by means of irradiation at low temperatures with ${\mathrm{He}}^{+}$ ions. The maximum transition temperature obtained is 3.2 K. It is shown that the presence of a special kind of defects produced during the irradiation is a necessary precondition for the occurrence of superconductivity.