The Bloch state of positronium in alkali halide crystals is considered. Tnt,eractions of positronium with the crystal field and with acoustic phonons are taken into account using perturbation theory. The effective mass of positronium in alkali halides is determined theoretically for the first time. Influence of these interactions on the positronium features in a crystal is discussed.

No abstract

No abstract

The positron annihilation method is effectively used in studying radiationinduced defects in solids, in particular f o r semiconductor crystals. In /1 to 31 the positron mean lifetime was measured at low temperatures after high temperature annealing of Si crystals irradiated by neutrons, electrons, and protons.12 Ge p-type crystals of Q = 35 ! J cm, Ga doped (NGa = 6.7xlO ~m -~) have been studied in the present note. These crystals have been irradiated by 4.4 MeV electrons f r o m the "Microtrone" accelerator (fluence 0 = 9 . 7 6~x l 0 nealing has been carried out.

The localized positronium-like states in ionic crystals are considered as positron-electron pair bound states in the Coulomb field of the charge 2. The system characteristics are evaluated as a function of the magnitude 2. The calculated data are in agreement with the experimental ones in alkali halides for charges Z < 0.7. The properties and the formation possibility of the positronium-like states in ionic crystals are discussed.