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Title: Element specificity of ortho-positronium annihilation for alkali-metal loaded SiO{sub 2} glasses

Momentum distributions associated with ortho-positronium (o-Ps) pick-off annihilation photon are often influenced by light elements, as, e.g., carbon, oxygen, and fluorine. This phenomenon, so-called element specificity of o-Ps pick-off annihilation, has been utilized for studying the elemental environment around the open spaces. To gain an insight into the element specificity of o-Ps pick-off annihilation, the chemical shift of oxygen 1s binding energy and the momentum distributions associated with o-Ps pick-off annihilation were systematically investigated for alkali-metal loaded SiO{sub 2} glasses by means of X-ray photoelectron spectroscopy and positron-age-momentum correlation spectroscopy, respectively. Alkali metals introduced into the open spaces surrounded by oxygen atoms cause charge transfer from alkali metals to oxygen atoms, leading to the lower chemical shift for the oxygen 1s binding energy. The momentum distribution of o-Ps localized into the open spaces is found to be closely correlated with the oxygen 1s chemical shift. This correlation with the deepest 1s energy level evidences that the element specificity of o-Ps originates from pick-off annihilation with orbital electrons, i.e., dominantly with oxygen 2p valence electrons and s electrons with lower probability.
Authors:
 [1] ;  [2]
  1. Department of Environmental Sciences, Tokyo Gakugei University, 4-1-1 Koganei, Tokyo 184-8501 (Japan)
  2. Japan International Research Center for Agricultural Sciences, Tsukuba, Ibaraki 305-8686 (Japan)
Publication Date:
OSTI Identifier:
22416220
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 142; Journal Issue: 9; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ALKALI METALS; ANNIHILATION; ATOMS; BINDING ENERGY; CARBON; CHEMICAL SHIFT; CHEMICAL STATE; CORRELATIONS; ELECTRONS; ENERGY LEVELS; FLUORINE; GAIN; OXYGEN; PHOTONS; POSITRONIUM; POSITRONS; SILICON OXIDES; SPECIFICITY; VISIBLE RADIATION; X-RAY PHOTOELECTRON SPECTROSCOPY