The lifetimes of the first excited states of ${\mathrm{B}}^{10}$ and ${\mathrm{Al}}^{28}$ have been measured by a recoil technique which incorporates coincidence counting. Recoil nuclei are produced in a unique manner which facilitates an accurate determination of the recoil velocity. Corrections to the velocity for target thickness were investigated experimentally. Lifetimes of (8.5±2.0)×${10}^{-10\mathrm{}}$ sec and (3.0±0.5)×${10}^{-9\mathrm{}}$ sec were obtained for the first excited states of ${\mathrm{B}}^{10}$ and ${\mathrm{Al}}^{28}$, respectively.

• Received 6 September 1956

DOI:https://doi.org/10.1103/PhysRev.104.1612