Single‐crystal Si has been implanted with O+ions at 2 MeV energy, to doses from 0.1 to 2×1018O+ cm−2and at substrate temperatures between 90 K and 700 °C. Infrared reflection spectra in the transparent region 1500–7000 cm−1were measured and interference fringes were observed. A detailed theoretical analysis of the interference fringes yields refractive index profiles which provide accurate measurements of the range and straggle of the implanted ions, the Si overlayer crystallinity, and the oxygen concentration depth profile. The implantation temperature influences the crystallinity of the Si overlayer but not the oxygen distribution. The measured range parameters are in agreement with theory. The 2 MeV results are compared to results from 200 and 90 keV implants, which show that the method is applicable for a wide range of separation by implantation of oxygen structures. Rutherford backscattering spectroscopy and ion channeling results are in good agreement with the infrared results. It is concluded that infrared spectroscopy is the most convenient and inexpensive nondestructive technique to investigate structures formed by MeV and lower‐energy O+implantation. ©1995 American Institute of Physics.