Radiations fromBr77andNi57

The nuclear spectra of ${\mathrm{Br}}^{77}$ (58 hr) and ${\mathrm{Ni}}^{57}$ (36 hr) have been investigated in a magnetic lens spectrograph. ${\mathrm{Br}}^{77}$ decays by orbital electron capture and positron emission to ${\mathrm{Se}}^{77}$. ${\mathrm{Br}}^{77}$ emits a single positron group of energy 0.336 Mev together with gamma-rays of energy 0.160, 0.237, 0.284, 0.298, 0.520, 0.641, and 0.813 Mev, of which the lines at 0.160, 0.237, and 0.520 Mev are internally converted. ${\mathrm{Br}}^{77}$ is the parent of the metastable state ${\mathrm{Se}}^{77m}$ of 17-sec half-life, and the energy of the gamma-ray associated with this transition is 0.160 Mev.