Probing the site-specific annihilation of positrons in a nanocomposite medium by 2-detector Doppler broadening measurements

Using the 2-detector coincidence set-up, the Doppler broadened spectra of p ositron annihilation radiation from a silver-polymer nanocomposite has been recorded with significantly reduced background. This enabled to analyse th e Gaussian wings of the spectra, populated by events due to the annihilatio n with higher momentum core electrons. The signals from the silver nanopart icles embedded in the polymer were found to appear under a characteristic p eak at the Doppler shifted energy corresponding to pure silver. (C) 2000 Pu blished by Elsevier Science B.V. PACS: 61.46. + w; 71.24. + q; 71.60. + z; 78.70.Bj.