Time dependent diffusion and annihilation of positrons
- Institut fuer Nukleare Festkoerperphysik, Universitaet der Bundeswehr, Muenchen, D-8014 Neubiberg (Germany)
The time-dependent diffusion equation of positrons implanted epithermally in a semi-infinite solid has been solved using a Green's function method. Subsequent lifetime spectra, deriving from the annihilation of free thermal and surface trapped positrons, and from para-Ps, have been modeled. The resulting curves resemble a sum of two exponential components. Because of the very short times involved, the contribution due to non-thermal positrons reaching the surface is much less significant than for steady-state models. At room temperature reflection of thermal positrons at the surface has very little effect on the solution to the diffusion equation. For strongly reflecting surfaces the sink and annihilation rates are qualitatively similar to those for a transparent surface, although strongly reduced.
- OSTI ID:
- 5020882
- Report Number(s):
- CONF-900798-; CODEN: APCPC
- Journal Information:
- AIP Conference Proceedings (American Institute of Physics); (United States), Vol. 218:1; Conference: 4. international workshop on slow-positron beam techniques for solids and surfaces, London (Canada), 3-6 Jul 1990; ISSN 0094-243X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
POSITRONS
ANNIHILATION
DIFFUSION
SOLIDS
POSITRON COLLISIONS
GREEN FUNCTION
LIFETIME
POSITRONIUM
SURFACE PROPERTIES
TIME DEPENDENCE
TRAPPING
ANTILEPTONS
ANTIMATTER
ANTIPARTICLES
BASIC INTERACTIONS
COLLISIONS
ELECTROMAGNETIC INTERACTIONS
ELEMENTARY PARTICLES
FERMIONS
FUNCTIONS
INTERACTIONS
LEPTONS
MATTER
PARTICLE INTERACTIONS
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654001 - Radiation & Shielding Physics- Radiation Physics
Shielding Calculations & Experiments
656003 - Condensed Matter Physics- Interactions between Beams & Condensed Matter- (1987-)