Accession Number : AD0613582

Title :   ANNIHILATION OF POSITRONS IN METALS.

Descriptive Note : Doctoral thesis,

Corporate Author : CALIFORNIA UNIV SAN DIEGO LA JOLLA

Personal Author(s) : Majumdar,Chanchal Kumar

Report Date : 05 FEB 1965

Pagination or Media Count : 307

Abstract : The theory of positron annihilation in metals, including electron-positron and electron-electron interaction, is discussed. It is well-known that the Coulomb force of the positron causes very major changes in the motion of the electrons. It is established that a sharp 'break' in the angular correlation curve of the two gamma-rays resulting from singlet state annihilation occurs at precisely those angles where it should be expected in the absence of electron-positron interaction. This makes positron annihilation in metals a useful tool for the investigation of the true Fermi surface. Taking advantage of such a break in the angular correlation curve, a simple experiment is proposed to measure the effective mass of the positron in metals. The experiment consists in a study of the temperature dependence of the angular correlation curve. It is found that an electron-positron bound state or a positronium-like state does not exist in metals. A more general result is derived: in a noninteracting electron gas in the presence of a localised external potential, there is no sharp distinction between bound and unbound states. (Author)

Descriptors :   (*POSITRONS, ANNIHILATION REACTIONS), (*ANNIHILATION REACTIONS, METALS), POSITRONIUM, ELECTRONS, CORRELATION TECHNIQUES, PERTURBATION THEORY, TEMPERATURE, FERMIONS

Distribution Statement : APPROVED FOR PUBLIC RELEASE