Swift-uranium-ion-induced damage in sapphire

Single crystals of {α}-Al₂{O}₃$ were irradiated at Ganil with $²³⁸U$ ions using four different energies: 0.48, 1.72, 2.78, and 3.40 MeV/u. All the irradiations were performed at a temperature of {}80 K, with fluences extending from 1.2×{}10¹² to 2.5×{}10¹² ions cm^-2. The samples were characterized by Rutherford backscattering spectrometry in channeling geometry (RBS-C) and optical absorption measurements. RBS-C analyses evidence the lattice disorder induced by collective electronic excitations. Depending on the electronic stopping power (dE/dx)e (up to 44.2 keV nm^-1), the damage cross section Aₑ varies between 0.3 and 2.1×{}10^-13 cm². Optical absorption spectroscopy exhibited the characteristic bands associated with oxygen vacancies. The kinetics of F centers were determined in order to precisely determine the respective contributions of the nuclear and electronic processes in point-defect generation.