Efficient radiative defects are introduced in silicon by annealing at 450 °C. They are associated with very sharp and intense transitions at 0.926 eV (Hline) and at 0.767 eV (Pline). A close correlation has been established between the intensity of these lines and the oxygen content of the sample. The carbon content correlates also with the lineH. It is shown that the radiation induced lines at 0.79 eV (Cline) and at 0.97 eV (Gline) are similarly influenced by the oxygen and carbon content. Although the detailed nature of the centers responsible forHandPlines is not known it can be put forward that their formation is controlled by Oimigration, and that the center leading toHmust be similar to theGcenter (CSi–Sii−CSi).