Pressure Dependence of Positron Annihilation in Alkali Metals

1975 ◽  
Vol 53 (5) ◽  
pp. 450-454 ◽  
Author(s):  
P. Kubica ◽  
M. J. Stott
Keyword(s):  
Positron Annihilation ◽  
Angular Correlation ◽  
Pressure Dependence ◽  
Alkali Metals ◽  
Correlation Data

The observed pressure dependence of the total positron annihilation rates in alkali metals has been studied. The observation that the rates increase more rapidly with pressure than the estimated valence annihilation rates alone has been explained in terms of increased positron penetration into the ion cores. This picture is shown to be consistent with observed changes with pressure in angular correlation data for Na.

Positron Annihilation with Core Electrons in the Noble Metals

1974 ◽  
Vol 52 (4) ◽  
pp. 336-339 ◽  
Author(s):  
E. H. Becker ◽  
A. G. Gould ◽  
E. M. D. Senicki ◽  
B. G. Hogg
Keyword(s):  
Simple Model ◽  
Fermi Surface ◽  
Single Crystals ◽  
Positron Annihilation ◽  
Angular Correlation ◽  
Noble Metals ◽  
Correlation Data ◽  
Core Electrons

Experimental angular correlation curves for identically oriented single crystals of copper, silver, and gold have been obtained using "a point geometry" apparatus. The differences between these angular correlation data are compared to the differences predicted using a simple model of the Fermi surface combined with calculations of the theoretical core distributions.

Positron Annihilation in Teflon and Polyethylene

1974 ◽  
Vol 52 (11) ◽  
pp. 935-939 ◽  
Author(s):  
Donald P. Kerr
Keyword(s):  
Angular Distribution ◽  
Positron Annihilation ◽  
Angular Correlation ◽  
Gamma Rays ◽  
Momentum Distribution ◽  
Angular Distributions ◽  
Distribution Data ◽  
Lifetime Component ◽  
Considerable Uncertainty ◽  
Correlation Data

Both the time spectra and the angular distributions of the annihilation gamma rays have been measured for positrons annihilating in Teflon and polyethylene in an attempt to clarify which annihilation mechanisms account for the various lifetimes in these materials. Some authors have suggested that, in addition to the longest lifetime component, one of the shorter lived components also arises from the pickoff annihilation of orthopositronium. If this were the case, substantially more positronium would be formed than is indicated by the intensity of the longest lived component alone, and should be detectable through a measurement of the intensity of the low momentum portion of the momentum distribution obtained from the angular correlation data. In the present work, four lifetimes are apparent in the time spectra although there is considerable uncertainty in resolving the two shortest components. The angular distribution data, in both cases, yielded a low momentum component whose intensity indicates that only the longest lifetime component arises from pickoff annihilation of orthopositronium. The three shorter lifetime components are discussed.

Topological Quasi-Positroniums in Graphite-Alkali Metal Intercalation Compounds

2012 ◽  
Vol 733 ◽  
pp. 115-118 ◽  
Author(s):  
Makoto Saito ◽  
Kouhei Yamada ◽  
Ikuzo Kanazawa
Keyword(s):  
Alkali Metal ◽  
Positron Annihilation ◽  
Angular Correlation ◽  
Intercalation Compounds ◽  
Theoretical Formula ◽  
Narrow Component ◽  
Second Stage ◽  
Correlation Data

We have analyzed the positron annihilation Angular Correlation data in the second stage graphite-potassium intercalation C24K with the theoretical formula extended from "topological quasi-positronium model" and have proposed one of the possible origins of the anisotropic narrow component in alkali-metal graphite intercalations compounds (AGICs).

Pressure Dependence of Positron Annihilation Rates in the Alkali Metals

1971 ◽  
Vol 27 (9) ◽  
pp. 580-582 ◽  
Author(s):  
I. K. MacKenzie ◽  
R. LeBlanc ◽  
B. T. A. McKee
Keyword(s):  
Positron Annihilation ◽  
Pressure Dependence ◽  
Alkali Metals

Investigation of Polymer Relaxation after Deformation by Positron Annihilation

1992 ◽  
Vol 247 ◽  
Author(s):  
Sergey A. Tishin ◽  
Mihail I. Tsapovestsky ◽  
Vladimir A. Tishin ◽  
Vladimir N. Kestelman
Keyword(s):  
Positron Annihilation ◽  
Angular Correlation ◽  
Life Time ◽  
Slow Relaxation ◽  
Dielectric Losses ◽  
Free Film ◽  
Axial Tension ◽  
Polymer Relaxation ◽  
Sample Density ◽  
Nonmonotonic Change

ABSTRACTThe relaxation of polyimid films after the axial tension has been investigated by measuring life-time of positrons and angular correlation of annihilation photons. The nonmonotonic change of mean life-time while relaxing the free film has been found. Two range of changes of positron-sensitive properties can be seen: “rapid” relaxation for 4–5 hours (characterized by reducing life-time of short-lived component) and “slow” relaxation (characterized by reducing the intensity of long-lived component). The results of this investigation have been compared with those of measuring of sample density and dielectric losses. The possible explanations and the- changes of mechanizms of relaxation with the conditions of deformation and “the rest” of polymers are analyzed.

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