MOMENTUM DISTRIBUTIONS OF TWO PHOTON ANNIHILATING POSITRON–ELECTRON PAIRS IN HEXANE AND DECANE

1967 ◽  
Vol 45 (12) ◽  
pp. 3895-3900 ◽  
Author(s):  
S. Y. Chuang ◽  
B. G. Hogg
Keyword(s):  
Wave Function ◽  
Positron Annihilation ◽  
Angular Correlation ◽  
High Precision ◽  
Atomic Carbon ◽  
Electron Pairs ◽  
Two Photon ◽  
Momentum Distributions ◽  
Positron Wave Function

Momentum distributions are calculated for electrons in the C–C and C–H bonds in hydrocarbons, using analytic SCF functions for atomic carbon orbitals and Heitler–London-type functions for the two paired electrons in the C–C and C–H bonds. The positron wave function is assumed to be a constant. The computed momentum distributions are then compared with high-precision experimental distributions obtained from positron-annihilation angular correlation experiments.

An experimental and theoretical study of the momentum distribution of two photon annihilating positron–electron pairs in methane

1968 ◽  
Vol 46 (20) ◽  
pp. 2309-2313 ◽  
Author(s):  
S. Y. Chuang ◽  
W. H. Holt ◽  
B. G. Hogg
Keyword(s):  
Wave Function ◽  
Ground State ◽  
Theoretical Study ◽  
Experimental Distribution ◽  
Electron Pairs ◽  
Two Photon ◽  
Momentum Plane ◽  
Radial Schrödinger Equation ◽  
Momentum Distributions ◽  
Positron Wave Function

The momentum distributions of annihilating positron–electron pairs have been measured in liquid and solid methane. Calculated momentum distributions generally assume that the positron wave function ψ+ = 1. This low-momentum, plane-wave representation of the positron is inadequate to describe the experimental distribution for high momenta. A ψ+ obtained by numerical integration of the ground-state radial Schrödinger equation is employed in the calculation and a good fit is observed with experiment for all momentum values.

Positron Annihilation and the Band Structure in Molybdenum

1972 ◽  
Vol 50 (15) ◽  
pp. 1777-1781 ◽  
Author(s):  
S. M. Kim ◽  
W. J. L. Buyers
Keyword(s):  
Wave Function ◽  
Band Structure ◽  
Angular Correlation ◽  
Room Temperature ◽  
Theoretical Calculations ◽  
Plane Waves ◽  
Interpolation Scheme ◽  
Accurate Representation ◽  
Two Photon ◽  
Positron Wave Function

Measurements have been made of the two-photon angular correlation from positrons annihilating in single-crystal molybdenum at room temperature. By means of a combination of conventional slits and Soller slits the number of annihilations for which the momentum lies along a line in the momentum distribution is obtained, and results are presented for the [ζ,ζ,0], [0,0,ζ, and [ζ,ζ,0.71] directions. Theoretical calculations of the angular correlation have been made based on the interpolation or pseudopotential scheme with s–d interaction included. The parameters of the interpolation scheme have been chosen so that an accurate representation is obtained of the APW band structure of Mattheiss. The positron wave function has been obtained in terms of 141 plane waves. The width of the calculated two-photon angular correlation is found to be much broader than the experimental width unless the relative s and d enhancement is considered.

MOMENTUM DISTRIBUTION OF METALLIC ELECTRONS BY POSITRON ANNIHILATION

1957 ◽  
Vol 35 (2) ◽  
pp. 168-183 ◽  
Author(s):  
A. T. Stewart
Keyword(s):  
Positron Annihilation ◽  
Momentum Distribution ◽  
Center Of Mass ◽  
Velocity Dependence ◽  
Conduction Electrons ◽  
Two Photon ◽  
Photon Decay ◽  
Electron Positron ◽  
Momentum Distributions ◽  
Annihilation Probability

The angular correlation of photons from the two-photon decay of positrons has been measured for positrons annihilating in some 34 elements, mostly metals. These data give the momentum distribution of photons and hence of the center of mass of the annihilating electron–positron pairs. The momentum distributions are discussed in terms of the velocity dependence of the annihilation probability. It is concluded that the observed momentum distributions are primarily the momentum distributions of the conduction electrons in the metals. A higher momentum component is observed, which is attributed to ion core effects.

Study of Single Crystals of Magnesium and Zinc by Positron Annihilation

1972 ◽  
Vol 50 (20) ◽  
pp. 2520-2522 ◽  
Author(s):  
E. H. Becker ◽  
E. M. D. Senicki ◽  
A. G. Gould ◽  
B. G. Hogg
Keyword(s):  
Wave Function ◽  
Single Crystals ◽  
Positron Annihilation ◽  
Enhancement Factor ◽  
Wave Functions ◽  
Theoretical Predictions ◽  
Positron Wave Function ◽  
Electronic Wave Functions ◽  
Simple Picture ◽  
Theory And Experiment

A point geometry positron annihilation angular correlation apparatus has been used to study oriented single crystals of magnesium and zinc. The results are compared with the theoretical predictions obtained from a simple picture of the electronic wave functions combined with two models for the positron wave function. The agreement between theory and experiment is considerably improved in the case of magnesium by the use of an enhancement factor.

Two-photon momentum density and angular correlation of positron annihilation radiation in Pd and PdH

1986 ◽  
Vol 34 (2) ◽  
pp. 853-858 ◽  
Author(s):  
Anjali Kshirsagar ◽  
D. G. Kanhere ◽  
R. M. Singru
Keyword(s):  
Positron Annihilation ◽  
Angular Correlation ◽  
Momentum Density ◽  
Annihilation Radiation ◽  
Photon Momentum ◽  
Two Photon

Effect of Positron Wave Function on Positron Annihilation Rates and Electron-Positron Momentum Densities in Solids

2001 ◽  
Vol 363-365 ◽  
pp. 603-605
Author(s):  
Anna Rubaszek ◽  
Z. Szotek ◽  
W.M. Temmerman
Keyword(s):  
Wave Function ◽  
Positron Annihilation ◽  
Electron Positron ◽  
Positron Wave Function

Angular correlation of two-photon positron annihilation in molecular hydrogen and nitrogen

1994 ◽  
Vol 89 (1) ◽  
pp. 319-324 ◽  
Author(s):  
A. S. Ghosh ◽  
T. Mukherjee ◽  
J. W. Darewych
Keyword(s):  
Positron Annihilation ◽  
Angular Correlation ◽  
Molecular Hydrogen ◽  
Two Photon

Positron annihilation in oriented single crystals of calcite: Two photon angular correlation

1980 ◽  
Vol 15 (1) ◽  
pp. 115-120
Author(s):  
P. Ramasamy ◽  
F. D. Gnanam ◽  
S. Krishnan ◽  
G. S. Laddha
Keyword(s):  
Single Crystals ◽  
Positron Annihilation ◽  
Angular Correlation ◽  
Two Photon
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