Oxygen-rich Ge samples were bombarded with fast electrons (E=4 MeV) at 80 °C and subjected to isochronal (100–340 °C) and isothermal (350 °C) annealing. Infrared absorption spectra were measured at room temperature. Preliminary irradiation of the samples is found to strongly enhance the development of the absorption bands in the range 600 to 780 cm⁻¹ when the Ge〈Sb,O〉 crystals are heated to 350 °C. The bands are assigned to local vibrational modes of thermal donors. It is inferred from the annealing studies that a radiation-induced complex with the local vibrational modes at about 770–780 cm⁻¹ is probably responsible for the enhanced growth of the thermal donors. Oxygen dimers are proposed as such a complex.