Radiation damage in magnesium oxide single crystals by positive ion irradiation

The spatial profile of radiation damage in MgO single crystals for 1.5 MeV H+ ions was compared with the calculated nuclear stopping power profile. The number of anion vacancies produced in MgO by 0.5 and 2.0 MeV H+ and He+ ions was obtained from the optical absorption and F and F+ bands at 250 nm. This was considerably lower than the calculated values. The spontaneous recombination of vacancies and interstitials having separations less than a unique ''critical distance'' was investigated and found to be inadequate to account for this discrepancy. Study of a recently proposed thermal spike mechanism indicates that thermally excited defect diffusion is consistent with the experimental results within a rather large uncertainty