Formation of substitutional hydrogen centers in LiF:OH crystals

ESR and infrared absorption are measured on neutron‐irradiated LiF:OH crystals. In unirradiated specimens an sharp absorption at 2.8 μ;m is observed and attributed to OH − ions coupled to a Mg impurity. After neutron irradiation the 2.8 μm band disappears and a broad band appears at 1930 cm −1 . When the irradiated crystal is annealed at higher temperatures, the 1930 cm −1 band increases a little and then decreases. In parallel with the decay of the 1930 cm −1 band, another absorption band grows peaking at 1013 cm −1 , which is attributed to U centers in LiF. H 0 centers are observed by ESR in neutron‐irradiated crystals. On annealing at higher temperatures the H 0 centers increase as the 1013 cm −1 band grows. While the 1013 cm −1 band increases monotonously with temperature, the H 0 centers decrease above 270 °C. It is concluded that hydrogen centres are produced by dissociation of OH‐ ions in neutron‐irradiated LiF:OH crystals and that immediately after irradiation U centers do not exist, which are formed in the course of annealing from the precursor suggested to be U 1 centers and afterwards from H 0 centers.