A revised decay scheme of the 16-minute isomer ${\mathrm{Ta}}^{182m}$ involves three states of ${\mathrm{Ta}}^{182}$ at excitation energies of 147 kev, 319 kev, and 503 kev. Transition multipolarities were classified by measuring both gamma-ray coincidences and internal conversion electrons. The 503-kev isomeric state decays mainly (98%) by a 184-kev $E3\mathrm{}$ transition to the 319-kev state. This 319-kev state decays mainly (94%) to the 147-kev state by means of a 172-kev transition that is predominantly $M1\mathrm{}$. The 147-kev transition to the ground state is also predominantly $M1\mathrm{}$. Two of the three possible crossover transitions were observed; a 356-kev $M4\mathrm{}$ transition originates at the isomeric level and a 319-kev $E2\mathrm{}$ transition connects the second excited state with the ground state.

The 147-kev and the 319-kev states are probably the first and second excited rotational states of the ground-state configuration. The relevant rotational parameters are of particular interest because very little is known about moments of inertia for odd-odd nuclei.

The relative probabilities were determined for pile neutron activation of the 16-minute isomer, ${\mathrm{Ta}}^{182m}$, and the 112-day ground state, ${\mathrm{Ta}}^{182}$. If the ground-state formation cross section is taken as 21 barns, the corresponding value for the isomer is only 9 mb.

• Received 5 July 1960

DOI:https://doi.org/10.1103/PhysRev.121.1158