BERICHTIGUNGEN

around 340 C K. In the second heating run (curve 2) the 420 °K peak is considerably suppressed and two well defined peaks around 340 and 360 C K appear. The peak positions on the tempe-rature scale were found to remain unchanged in the subsequent heating runs (curve 3). It is now generally accepted that the plastic defor-mation of alkali halide crystals gives rise to dislocation debris in the form of vacancy clusters and dislocation dipoles 3 ~ 5 . It is therefore presumed that the centre responsible for 420 °K glow peak is a complex formed by the association of a TI ion with a single vacancy or an aggregate of vacancies, the complex being situat-ed in the dislocation region. At the end of the first heatinig run, when the specimen is heated to around 500 °K, a change in the distribution of the dislocations would take place to lower the strain energy of the microcrystals. Such a redistribution may involve both