Measurements of total cross-sections for positron- and electron-alkali atom scattering and of positronium formation cross-sections for argon and potassium atoms

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:7072142

Parikh, S P

The author has measured total cross sections (Q[sub T's]) for positrons (e[sup +]'s) and electrons (e[sup [minus]]'s) scattering from potassium (K) and rubidium (Rb) atoms and for e[sup [minus]]'s scattering from lithium (Li) and cesium (Cs) atoms, using a beam transmission technique. The measured e[sup [minus]]-alkali atom Q[sub T]'s show a monotonic decrease with increasing energy for all the alkali atoms. The measured e[sup +]-K and -Rb Q[sub T]'s each show a peak in the vicinity of 5 eV and decrease substantially as the e[sup +] energy is reduced below 6 eV, in sharp contrast to the results obtained in recent 5 state close coupling approximation calculations. The author has made preliminary measurements of positronium (Ps) formation cross sections (Q[sub Ps]) for e[sup +]-Ar and K collisions. The experimental approach involves setting lower and upper limits on Q[sub Ps], using a combination of (1) detecting the coincidences of 511 keV annihilation gamma rays produced by the decay of para-Ps and by the interaction of ortho-Ps with the wall of the scattering cell and (2) determining the scattering cross sections associated with the measured transmission of the e[sup +] beam through the gas in the scattering cell with the angular discrimination of the apparatus deliberately made as poor as possible. The constraints placed by these lower and upper limits are used to check for consistency with prior experimental and theoretical results for Ar and to provide measurements of Q[sub Ps] for K which are compared with available theoretical results.

• Research Organization: Wayne State Univ., Detroit, MI (United States)
• OSTI ID: 7072142
• Country of Publication: United States
• Language: English

Related Subjects

664300* -- Atomic & Molecular Physics-- Collision Phenomena-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
ALKALI METALS
ANTILEPTONS
ANTIMATTER
ANTIPARTICLES
ARGON
ATOM COLLISIONS
CESIUM
COLLISIONS
CROSS SECTIONS
ELECTRON COLLISIONS
ELECTRON-ATOM COLLISIONS
ELECTRONS
ELEMENTARY PARTICLES
ELEMENTS
FERMIONS
FLUIDS
GASES
LEPTONS
MATTER
METALS
NONMETALS
POSITRONIUM
POSITRONS
POTASSIUM
RARE GASES
RUBIDIUM
SCATTERING
TOTAL CROSS SECTIONS