Dynamics of replacement sequences and of crowdions

The theory of the formation of point defects by ionization in alkali halides has been extended to include the dynamics of the subsequent motion of replacement sequences and of crowdions (H-centers) at low temperatures. Particular attention is paid to the stochastic aspect of the motion of these centers, which appears to play a crucial role in intepreting recent experimental studies of interaction processes of H-centers with other defects in alkali halides. It turns out that at not too low temperatures the rate controlling reaction is the rotation of the centers. A detailed analysis of the kinetics of the various competing processes is given. (author)