Decay ofCo55; Levels inFe55

The decay of 18-h ${\mathrm{Co}}^{55}$ → ${\mathrm{Fe}}^{55}$ has been re-examined with a magnetic beta spectrometer and a Ge(Li) detector. It has been established that both the 1316.4-keV and 411.4-keV levels are populated in the gamma cascades. Positron emission and electron capture populate the 1408.4-keV level (36%), the 1316.4-keV level (5%), and the 931.2-keV level (54%). The remaining 5% of the decay populates seven levels above 1408 keV. Positron decay to the 411-keV level and to the ground state in sum is ${10}^{-5\mathrm{}}$ per disintegration. From the endpoint of the maximum-energy positron group, $E_0=(1513\mathrm{}\pm 2)$ keV, feeding the 931.2-keV gamma ground-state transition, the total decay energy is found to be (3466±2) keV. The decay scheme requires only levels already known in ${\mathrm{Fe}}^{55}$ from nuclear reaction studies. A survey of the reaction data and the decay information reveals that the only conflict is the assignment of $l=4\mathrm{}$ (from some of the ${\mathrm{Fe}}^{54}\mathrm{}(d,p)\mathrm{}{\mathrm{Fe}}^{55}$ studies) to the level at 2589 keV.