Transformations of Absorption and Emission Centers in ${\hbox {PbWO}} _{4}$

Non-stoichiometric PWO crystals were studied at annealing experiments in various atmospheres. It was found that a substantial part of absorption centers in the PWO platelets was brought into absorption activity due to mechanical processing of their surfaces. The green emission of the type G(II) is conditioned by presence of mechanical tension at the emission centers. A new process found at annealing is the transformation of the 330/355 centers into the 340/430 centers caused by separation of lead vacancies from the former ones.