Accession Number : AD0286667

Title :   POSITRON ANNIHILATION REACTIONS IN CONDENSED MATERIALS

Corporate Author : WESTERN RESERVE UNIV CLEVELAND OHIO

Personal Author(s) : MCGERVEY,JOHN D.

Report Date : 30 JUN 1962

Pagination or Media Count : 1

Abstract : Measurements were made of the time distribution of positron annihilations in aluminum, tin, copper, titanium, and zinc. All of the metals measured to date have shown a long lived component. This component, which is still unexplained, contains from 5 to 10% of the total counts, with A MEAN LIFE OF ABOUT 4 X 10 TO THE -10TH POWER SEC IN ALL THE METALS MEASURED. The presence of the long lived component is deduc small number of counts. Nevertheless these counts are significantly above the background level the counting rate in the peak was about 5000 times the background. Short mean lives in these metals were determined by subtracting the counts in the extrapolated long lived component and measuring the slope of t e remaining distribution. Data are being obtained on the angular distribution of annihilation radiation from alloys. The angular correlation method gives a direct expd from an extremely small number of counts. Nevertheless these counts are significantly above the background level the counting rate in the peak was about 5000 times the background. Short mean lives in these metals were determined by subtracting the counts in the extrapolated long lived component and measuring the slope of t e remaining distribution. Data are being obtained on the angular distribution of annihilation radiation from alloys. The angular correlation method gives a direct experimental determination of the Fermi energy of the conduction electrons. The major difficulty with the method is that in many alloys of interest a large number of positrons annihilate with core electrons rather than conduction electrons, and it is necessary to subtract this component in order to obtain the curve for conduction electron annihilation. (Author)

Descriptors :   *ANNIHILATION REACTIONS, *ATOMIC STRUCTURE, *POSITRONS, ALLOYS, ALUMINUM, BRASS, COPPER, COUNTING METHODS, PULSE ANALYZERS, RADIOACTIVE ISOTOPES, SODIUM, TIN, TITANIUM, ZINC

Distribution Statement : APPROVED FOR PUBLIC RELEASE