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Positron annihilation in lattice defects of potassium chloride

Technical Report ·
OSTI ID:7332818
The angular correlation between annihilation quanta of positrons annihilating in pure and additively colored potassium chloride single crystals was measured up to color center concentrations of 6.1 x 10/sup 18//cm/sup 3/. A narrow component with 5.3 mrad fwhm was found in the correlation curves of samples containing more than approximately 10/sup 17/ F-centers/cm/sup 3/. It is shown that F- and M-centers are responsible for the occurrence of the narrow component. The shape and intensity of the latter can easily be calculated from the assumption that positrons are captured by F-center electrons to form localized positronium-like states at the negative-ion vacancies. Least-squares fits of this model to the experimental data yield a localization length of 5.48 + or - 0.05 A and a capture cross section of order 10/sup -15//cm/sup 2/. This supports the hypothesis of positronium formation. The enhancement of the narrow component due to magnetic mixing of the m = 0 eigenstates of singlet and triplet positronium was measured in external fields up to 25 kGauss with the field parallel and antiparallel to the polarization of the positrons, respectively. The observed effect confirms the existence of a positronium-like state and yields information about the probability density of the positron at the electron, the pick-off annihilation rate, and the degree of polarization of the positrons emitted by the /sup 22/Na source. (auth)
Research Organization:
Eidgenoessische Technische Hochschule, Zurich (Switzerland)
OSTI ID:
7332818
Report Number(s):
N-75-27934; DISS-4970
Country of Publication:
United States
Language:
English

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Related Subjects

36 MATERIALS SCIENCE
360603* -- Materials-- Properties
640303 -- Atomic
Molecular & Chemical Physics-- Positronium
Muonium
& Muonic & Mesic Atoms & Molecules
74 ATOMIC AND MOLECULAR PHYSICS
ABSORPTION
ALKALI METAL COMPOUNDS
ANGULAR CORRELATION
ANNIHILATION
ANTILEPTONS
ANTIMATTER
ANTIPARTICLES
BASIC INTERACTIONS
CHLORIDES
CHLORINE COMPOUNDS
COLLISIONS
COLOR CENTERS
CORRELATIONS
CROSS SECTIONS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
CRYSTALS
ELECTROMAGNETIC INTERACTIONS
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
F CENTERS
FERMIONS
GAMMA RADIATION
HALIDES
HALOGEN COMPOUNDS
INTERACTIONS
IONIZING RADIATIONS
LATTICE PARAMETERS
LEAST SQUARE FIT
LEPTONS
M CENTERS
MAXIMUM-LIKELIHOOD FIT
MONOCRYSTALS
NUMERICAL SOLUTION
POINT DEFECTS
POSITRON COLLISIONS
POSITRONIUM
POSITRONS
POTASSIUM CHLORIDES
POTASSIUM COMPOUNDS
PROBABILITY
RADIATIONS
VACANCIES