Manganese-53 has been produced by the nuclear reaction ${\mathrm{Cr}}^{53}(p, n){\mathrm{Mn}}^{53}$ in the bombardment of enriched ${\mathrm{Cr}}^{53}$ for a period of 8 hours with 9.5-Mev protons. Measurements of the decay and absorption data indicate that this nuclide is an orbital electron capturing activity without gamma rays or positrons. With the assumption that the cross section for the reactions ${\mathrm{Cr}}^{53}(p, n){\mathrm{Mn}}^{53}$ and ${\mathrm{Cr}}^{54}(p, n){\mathrm{Mn}}^{54}$ are the same, it is possible to calculate an approximate half-life of 140 years for this nuclide. These data together with those from previous measurements on the energy levels of ${\mathrm{Cr}}^{53}$ indicate that ${\mathrm{Mn}}^{53}$ probably decays from an $F_{\frac{5}{2}}$ ground state to a $p_{\frac{3}{2}}$ ${\mathrm{Cr}}^{53}$ ground state in an $l$-forbidden transition with a relatively high $log\mathrm{ft}$ value.

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