Positron and positronium in Al₂O₃ nanopowders Free

Software that allows fitting positron lifetime (LT) and coincidence Doppler broadened (CDB) positron annihilation spectra of nanodispersed dielectric powders is developed. Computer program takes into account following effects: possibility of e⁺ trapping by vacancy-type defects, formation of the surface-bound e⁺ states, formation and thermalization of Ps atoms in inter- granular space. In order to test the developed software, lifetime and coincident Doppler broadened spectra of Al₂O₃ nanopowders with different grain sizes are acquired. Suggested physical model of the processes involved gives self-consistent interpretation of the spectra. Parameters of the thermalization kinetics of Ps and its ortho-para conversion due to presence of O₂ molecules adsorbed on the crystallite surface are obtained.