Proton Induced Radioactivity of Manganese

The reaction ${\mathrm{Cr}}^{52}\mathrm{}(p,n)\mathrm{}{\mathrm{Mn}}^{52}$ at 6.6-Mev proton energy produces isomers with period 21.3 min. and 6.5 days. These are positron emitters with maximum positron energy of 2.2 Mev (21 min.) and 0.77 Mev (6.5 day). The gamma-ray spectrum for each isomer has been investigated. There are 2 gamma-rays per positron in the short period activity. The gamma-radiation in the 6.5-day activity is so intense that 95 percent of these disintegrations must be due to $K$-electron capture; this is followed by emission of probably two gamma-rays. In the remaining 5 percent the positron emission is followed by three gamma-rays. The threshold for the 21-min. activity and the yield for both periods have been determined.