Positron Spectra ofCo56

The positron spectrum of ${\mathrm{Co}}^{56}$ has been carefully studied with a magnetic spectrometer. Two positron groups were observed. The maximum energies and intensities of the two groups are 1.464±0.015 Mev and 0.440±0.030 Mev and ≥90% and ≤10%, respectively. No evidence for any other groups was found. In particular, an upper limit of 1% was set for the presence of any group with maximum energy 0.9-1.0 Mev. The high-energy spectrum has essentially an allowed shape. However, the inclusion of a shape factor such as ($1+\frac{0.3}{W}$) offers a more consistent fit to all the data.