Doppler broadening of positron annihilation radiation as a probe for the anisotropy of free‐volume‐holes in polymers
Author(s) -
Palacio C. A.,
Djourelov N.,
Kuriplach J.,
Dauwe C.,
Laforest N.,
Segers D.
Publication year - 2007
Publication title -
physica status solidi c
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.21
H-Index - 46
eISSN - 1610-1642
pISSN - 1862-6351
DOI - 10.1002/pssc.200675781
Subject(s) - doppler broadening , anisotropy , annihilation , annihilation radiation , positronium , spectral line , materials science , radiation , transverse plane , doppler effect , particle (ecology) , cuboid , molecular physics , volume (thermodynamics) , positron annihilation , atomic physics , nuclear magnetic resonance , positron , optics , physics , nuclear physics , electron , geometry , thermodynamics , oceanography , mathematics , structural engineering , astronomy , geology , engineering
Doppler broadening of annihilation radiation (DBAR) measurements have been performed in uniaxially hot‐drawn poly(methylmethacrylate) (PMMA) samples. The DBAR spectra were deconvoluted into three Gaussians. The full width at half‐maximum of the narrow component which is due to para‐Positronium (p‐Ps) self‐annihilation is under discussion. An anisotropy of the free volume holes (FVHs) has been detected by measuring the deformed samples at the stretching and transverse directions. The sample deformed at 280% was also measured as a function of the orientation angle (0°–90°) with respect to the stretching direction. The momentum distribution of p‐Ps, which is considered as a structureless particle confined in FVH of ellipsoidal or cuboid shape, was calculated as a function of the potential well size and depth and compared with experiment. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
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