Some aspects of the interactions of orthopositronium with perfect and defect surfaces of insulating materials
| Autor: | Danny Segers, Charles Dauwe, T. van Hoecke, B. Van Waeyenberge, Jan Kuriplach |
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| Rok vydání: | 1996 |
| Předmět: |
Quenching
Materials science Health Toxicology and Mutagenesis Public Health Environmental and Occupational Health Oxide Pollution Spectral line Analytical Chemistry Paramagnetism chemistry.chemical_compound Thermalisation Positron Nuclear Energy and Engineering chemistry Cluster (physics) Radiology Nuclear Medicine and imaging Irradiation Atomic physics Spectroscopy |
| Zdroj: | Journal of Radioanalytical and Nuclear Chemistry. 210:293-308 |
| ISSN: | 1588-2780 0236-5731 |
| DOI: | 10.1007/bf02056374 |
| Popis: | ETLA (Elastic Thermalisation Lifetime Analysis) is a new model function for the fitting of lifetime spectra of slowly thermalising orthopositronium in the free space between the grains of insulating oxide powders. From this model one can obtain three fundamental parameters; the mass of the cluster of atoms which scatters the o-Ps, the probability μ that the o-Ps is forced into two-quantum decay at each collision and the emission energyE(0) of the o-Ps from the powder surface. As a consequence of full thermalisation of the Ps it is shown that the o-Ps quenching constant λ q (℞) follows atT1/2 dependency for MgO, Al2O3 and SiO2 and for temperatures between 77 and 500 K. In MgO powder at low temperatures the irradiation by the positrons induces surface paramagnetic defects which are identified as Mg+ sites. These surface defects do not affect the thermalisation, but they induce paramagnetic o-p conversion i.e., an increase in μ, and they are also responsible for an increase in the emission energyE(0) of the o-Ps. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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