Br82mand Its Decay Scheme

The discovery of a new activity of bromine is reported and is assigned to a 2(-) isomeric state of ${\mathrm{Br}}^{82}$. The new activity is chemically identified as bromine and shown to be the short-lived parent of ${\mathrm{Br}}^{82}$. It decays primarily by a highly converted $M3\mathrm{}$ transition ($\alpha =382\mathrm{}\pm 75$) of 46 KeV to the 5(-) ground state of ${\mathrm{Br}}^{82}$. Two weak branches in the proposed decay scheme lead by beta emission to the 0.78-MeV level (0.15%) and the 1.48-MeV level (0.024%) of ${\mathrm{Kr}}^{82}$. Time-dependent gamma spectra, obtained with a large anticoincidence counter, demonstrate the growth of the 2.65-MeV sum peak of ${\mathrm{Br}}^{82}$ after thermal-neutron activation of N${\mathrm{H}}_4$Br. Short-lived gamma peaks at 46 keV, 0.78 MeV, and 1.48 MeV were observed in the gamma spectra of an activated sample of enriched N${\mathrm{H}}_4$Br (99.32% ${\mathrm{Br}}^{81}$). X-ray spectra of activated N${\mathrm{H}}_4$Br taken with an argon-methane proportional counter provide evidence that the short-lived component is a thermal-neutron activation product. One-component decay curves of the Br $K$ x rays over more than 6 half-periods define the half-life of ${\mathrm{Br}}^{82m}$ as 363±2 sec.