Decay of 18-minBr80

Abstract

Gamma rays with energies of 0.618±0.003, 0.640±0.009, 0.67±0.02, 0.710±0.010, 1.258±0.007, and 1.333±0.010 Mev have been observed in the decay of 18-min ${\mathrm{Br}}^{80}$, and their intensities determined. Of these, only the 0.618-Mev gamma ray has been previously reported. Two new levels are proposed at 1.26 and 1.33 Mev in ${\mathrm{Kr}}^{80}$, and the branching (crossover/cascade) determined for these levels as 0.46±0.08 and 0.14±0.06, respectively. The 0.67-Mev gamma ray is assigned to the first 2+ state of ${\mathrm{Se}}^{80}$, whose energy has been determined as 0.667±0.004 Mev from the ($p, p^{\prime }\gamma$) reaction. Excitation of the second level of ${\mathrm{Se}}^{80}$ at 1.44 Mev was not observed. The measured value of 0.62-Mev $\frac{\gamma }{{\beta }^{+}}$ of 2.6±0.1 has been used to evaluate $log\mathrm{ft}$ values for the transitions to various levels in ${\mathrm{Se}}^{80}$ and ${\mathrm{Kr}}^{80}$. The allowed transitions from the 1+ ground state of ${\mathrm{Br}}^{80}$ to the ground state and first two levels of both ${\mathrm{Se}}^{80}$ and ${\mathrm{Kr}}^{80}$ are found to be successively hindered, in accord with the empirical rule of Sakai.