A new isotope of hafnium, ${\mathrm{Hf}}^{182}$, has been produced by double neutron capture in ${\mathrm{Hf}}^{180}$ in the intense neutron flux of the materials testing reactor (MTR). Mass spectrometric analysis of the irradiated hafnium gave a ${\mathrm{Hf}}^{182}$/${\mathrm{Hf}}^{180}$ atom ratio of 0.00147±0.00001. The new isotope decays with a half-life of (9±2)×${10}^6$ years by ${\beta }^{-}$ emission predominantly to a 271-kev level in ${\mathrm{Ta}}^{182}$. The number of 271-kev gamma rays per ${\beta }^{-}$ disintegration is 0.84±0.10. The $log\mathrm{ft}$ for the beta transition to the ${\mathrm{Ta}}^{182}$ ground state is > 15 indicating that this transition is at least third forbidden. The neutron capture cross section of ${\mathrm{Hf}}^{181}$ is ${40}_{-20\mathrm{}}^{+40\mathrm{}}$ barns.

• Received 3 April 1961

DOI:https://doi.org/10.1103/PhysRev.123.1354