Studies of OH− and OD− Ions in Magnesium Oxide. I. Distribution and Annealing of Hydroxyl and Deuteroxyl Ions

Abstract

The infrared absorption and x-ray stimulated luminescence of magnesium oxide crystals containing OH− and OD− ions are reported. We find that the ratio ν(OH)− / ν(OD−) ≈ 1.35 determined from ir absorption data is very close to the expected theoretical value for pure stretching frequencies of the OH− and OD− ions. Comparison of the OH− and OD− spectra allows an unequivocal identification of the origin of three of the OD− bands. In particular a band at 2727 cm−1 is shown to be due to Mg(OD)2 precipitates, whereas the 2444.7- and 2455.5-cm−1 bands are due to the associate centers OD−[+ +] and OD−[+ +]O2−M3+. (In these linear systems [+ +] represents a cation vacancy, and M3+ represents a trivalent cation.) The effect of annealing treatments in the range 570–1500°K is discussed in the light of the distribution of OH− and OD− in the MgO lattice. Preliminary data on OH− absorption in CaO are also reported. The luminescence spectra from molecules of Mg(OH)2 and Mg(OD)2 in MgO are reported, and the associated fine structure is described as due to local vibrations of the molecule. The electronic states involved in the transition are not known.