Screening and Relativistic Effects on Beta Spectra
U.S. Atomic Energy Commission, Technical Information Branch, 1949 - Beta rays - 11 pages
In interpreting data on beta ray spectra, apparent deviations from the Fermi allowed form may be caused by neglect of the effect of screening by atomic electrons and by use of the nonrelativistic approximation to the Coulomb factor. The effect of the screening on the Coulomb factor h25 been calculated approximately for arbitrary Z, using a method based on the Thomas Fermi screened potential. The effect of screening is found to be an increase in the number of both positrons and electrons at low energies. Numerical results are given for S35, Cu64, and RaE. By use of a better approximation to the relativistic Coulomb correction factor, the error incurred by using the nonrelativistic form is estimated for various emitters. It is found that for sufficiently thin sources of Cu64 (for example) the neglect of the screening and relativistic effects contributes a considerable fraction of the apparent deviation from the Fermi theory.
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