THEORY OF POSITRON ANNIHILATION IN SODIUM FLUORIDE

Thesis/Dissertation · Mon Jan 01 04:00:00 EST 1962

OSTI ID:4741994

Ostrowsky, H S

A model of an ionic crystal of the Rocksalt structure was made by using free-ion Hartree-Fock electronic wavefunctions for the ions at each of the lattice points. This model is used to compute the wavefunction of a positron in the crystal on the assumption that the positron may be represented by a Bloch- type function not localized at any ion; positron-electron correlations are not considered. The interaction of the positron with the ions is calculated and used to determine the angular correlation of the gamma rays emitted in two-photon annihilation in the crystal. Numerical computations are carried out for polycrystalline NaF, and the resulting angular correlation curves are compared with experimental results. It is found that the model is qualitatively correct, but the theoretical distribution is too wide; it is suggested that the use of free-ion electronic wavefunctions accounts for the error, and that more accurate wavefunctions for ions in a crystal of this type should be computed. It is found that the positron wavefunction is only slightly inclined toward the negative ion, so that one may roughly estimate the proportion of the annihilation which takes place with each type of ion by comparing the volumes of the ions in the crystal. (Dissertation Abst., Vol. 23, No. 7)

• Research Organization: Originating Research Org. not identified
• NSA Number: NSA-17-017301
• OSTI ID: 4741994
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ANGULAR DISTRIBUTION
ANNIHILATION
BLOCH FUNCTION
BLOCH THEORY
CRYSTALS
ELECTRONS
GAMMA RADIATION
INTERACTIONS
IONS
LATTICES
MATHEMATICS
NUMERICALS
PHOTONS
PHYSICS
POSITRONS
QUANTUM MECHANICS
SODIUM FLUORIDES
VOLUME