Anomalous Enhancement in Defect Production in Gallium Irradiated by High-Energy Xenon Ions

Pure crystalline gallium samples have been irradiated at temperatures lower than 11 K with a high-energy Xe beam (27 MeV/a.m.u.) depositing 2 keV/Å by electronic excitations. The results obtained with the aid of resistance variation measurements are compared with those obtained by an electron irradiation and with published results on pure metals. For the first time in a pure crystalline metal, it is found that high-energy ions are more efficient than electrons or low-energy ions for defect creation. The role of displacement threshold anisotropy is discussed, and it is suggested that the high electronic stopping power is responsible for the observed effect.