An isomer of ${\mathrm{Co}}^{58}$ has been identified which decays with a half-life of 8.8 hours by emission of a 24.9±1.0 kev $\gamma$-ray. The ratio of the $K$ and $L$ conversion coefficients was 1.9±0.2. The relative cross section for formation of the isomeric and ground state of ${\mathrm{Co}}^{58}$ by $\alpha$-particle bombardment of manganese was found to be 1.7. The conversion coefficient of the 805 kev $\gamma$-ray of ${\mathrm{Fe}}^{58}$ was 2.5×${10}^{-4\mathrm{}}$. Possible decay schemes are presented.

• Received 28 April 1950

DOI:https://doi.org/10.1103/PhysRev.79.487