Physics – Condensed Matter – Statistical Mechanics
Scientific paper
Jan 1976
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1976stin...7618029c&link_type=abstract
Unknown
Physics
Condensed Matter
Statistical Mechanics
Gamma Rays, Line Spectra, Solar Flares, Statistical Mechanics, Charge Exchange, Maxwell-Boltzmann Density Function, Photons, Plasmas (Physics), Positron Annihilation, Positronium
Scientific paper
The gamma-ray line produced at 0.51-MeV was studied and is shown to be the result of either of free annihilation of positrons with electrons or of the decay of positronium by 2-photon emission. Positron annihilation from the bound state of positronium may also proceed by 3-photon emission, resulting in a continuum with energies up to 0.51-MeV. Accurate calculations of the rates of free annihilation and positronium formation in a solar-flare plasma are presented. Estimates of the positronium-formulation rates by charge exchange and the rates of dissociation and quenching are also considered. The temperature and density dependence of the ratio of 3-photon to 2-photon emission was obtained. It is shown that when the ratio of free electrons to neutral atoms in the plasma is approximately unity or greater, the Doppler width of the 0.51-MeV line is a function of the temperature of the annihilation region. For the small ion densities characteristics of the photosphere, the width is predominantly a function of the density.
Crannell Carol J.
Joyce Geoffrey
Ramaty Reuven
Werntz Carl
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