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Diffusion length of positrons and positronium investigated using a positron beam with longitudinal geometry

(2004) PHYSICAL REVIEW B. 70(11).
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Abstract
Positronium emission from single crystalline Al2O3, MgO and vitreous a-SiO2 surfaces was studied as a function of the positron implantation energy E by means of Doppler broadening spectroscopy and Compton-to-peak ratio analysis. When the Ge-detector is in-line with the positron beam, the emission of para-positronium yields a red-shifted fly-away peak with intensity I-pPs(e). An analysis of I-pPs(e) versus E for Al2O3 and MgO where no Ps is formed in the bulk (f(Ps)=0) results in positron diffusion lengths L+(Al2O3)=(18+/-1) nm and L+(MgO)=(14+/-1) nm, and efficiencies for the emission of Ps by picking up of a surface electron of f(pu)(Al2O3)=(0.28+/-0.2) and f(pu)(MgO)=(0.24+/-0.2). For a-SiO2 the bulk Ps fraction is f(Ps)(a-SiO2)=(0.72+/-0.01), f(pu)(a-SiO2)=(0.12+/-0.01) and the diffusion lengths of positrons, para-positronium and ortho-positronium are L+(SiO2)=(8+/-2)nm, L-pPs(SiO2)=(14.5+/-2) nm and L-oPs(SiO2)=(11+/-2)=nm. Depending on the specimen-detector geometry the emission of Ps at low implantation energy may cause either an increase or a decrease of the width of the annihilation line shape at low implantation energies.
Keywords
ENERGY POSITRONS, ANNIHILATION, EMISSION, QUARTZ, SPECTROSCOPY, SURFACES, CRYSTALS, DEFECTS

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Chicago
Van Petegem, Steven, Charles Dauwe, Toon Van Hoecke, Jérémie De Baerdemaeker, and Danny Segers. 2004. “Diffusion Length of Positrons and Positronium Investigated Using a Positron Beam with Longitudinal Geometry.” Physical Review B 70 (11).
APA
Van Petegem, Steven, Dauwe, C., Van Hoecke, T., De Baerdemaeker, J., & Segers, D. (2004). Diffusion length of positrons and positronium investigated using a positron beam with longitudinal geometry. PHYSICAL REVIEW B, 70(11).
Vancouver
1.
Van Petegem S, Dauwe C, Van Hoecke T, De Baerdemaeker J, Segers D. Diffusion length of positrons and positronium investigated using a positron beam with longitudinal geometry. PHYSICAL REVIEW B. 2004;70(11).
MLA
Van Petegem, Steven, Charles Dauwe, Toon Van Hoecke, et al. “Diffusion Length of Positrons and Positronium Investigated Using a Positron Beam with Longitudinal Geometry.” PHYSICAL REVIEW B 70.11 (2004): n. pag. Print.
@article{303151,
  abstract     = {Positronium emission from single crystalline Al2O3, MgO and vitreous a-SiO2 surfaces was studied as a function of the positron implantation energy E by means of Doppler broadening spectroscopy and Compton-to-peak ratio analysis. When the Ge-detector is in-line with the positron beam, the emission of para-positronium yields a red-shifted fly-away peak with intensity I-pPs(e). An analysis of I-pPs(e) versus E for Al2O3 and MgO where no Ps is formed in the bulk (f(Ps)=0) results in positron diffusion lengths L+(Al2O3)=(18+/-1) nm and L+(MgO)=(14+/-1) nm, and efficiencies for the emission of Ps by picking up of a surface electron of f(pu)(Al2O3)=(0.28+/-0.2) and f(pu)(MgO)=(0.24+/-0.2). For a-SiO2 the bulk Ps fraction is f(Ps)(a-SiO2)=(0.72+/-0.01), f(pu)(a-SiO2)=(0.12+/-0.01) and the diffusion lengths of positrons, para-positronium and ortho-positronium are L+(SiO2)=(8+/-2)nm, L-pPs(SiO2)=(14.5+/-2) nm and L-oPs(SiO2)=(11+/-2)=nm. Depending on the specimen-detector geometry the emission of Ps at low implantation energy may cause either an increase or a decrease of the width of the annihilation line shape at low implantation energies.},
  articleno    = {115410},
  author       = {Van Petegem, Steven and Dauwe, Charles and Van Hoecke, Toon and De Baerdemaeker, J{\'e}r{\'e}mie and Segers, Danny},
  issn         = {1098-0121},
  journal      = {PHYSICAL REVIEW B},
  keyword      = {ENERGY POSITRONS,ANNIHILATION,EMISSION,QUARTZ,SPECTROSCOPY,SURFACES,CRYSTALS,DEFECTS},
  language     = {eng},
  number       = {11},
  title        = {Diffusion length of positrons and positronium investigated using a positron beam with longitudinal geometry},
  url          = {http://dx.doi.org/10.1103/PhysRevB.70.115410},
  volume       = {70},
  year         = {2004},
}

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