Ionic and electronic processes during Frenkel defect annealing in KBr crystals above LHeT

The relaxation of radiation-induced optical absorption spectra and a set of thermally stimulated curves (current, depolarization current, diffusion current, emission-desorption of gas, thermal bleaching) of KBr crystals X-irradiated at 4.6 K are recorded synchronously or step by step. A multistage annealing of defects is detected: (i) from 4.6 to 32 K about ten substages controlled by the I centre delocalization are accompanied by electron and energy release, (ii) from 32 to 60 K about six substages controlled by the H centre delocalization are accompanied by corresponding electron and energy release and gas desorption peaks. A recombination of the migrating I or H centres within such complementary defect systems (pairs, triplets et al.) takes place:(i) (I...alpha), (I...F...V/sub k/), (I...F'...V/sub k/...V/sub k/), (ii) (H...F) and (H...F'...V/sub k/). Following phenomena in KBr at 4.6 K are observed and discussed: (i) the 'F-photostimulated' electron tunneling transfer within the excited pair (F*...H/sub A/) → (α...I/sub A/), (ii) the effect of dc field (3kV/cm) caused Frenkel defect formation efficiency increase (by >= 10%), (iii) the photoelectrical dissociation of the α centres. Comments about the anion Frenkel primary defect generation mechanisms are made. (author)