The following half-lives were measured: ${\mathrm{B}}^{12}$, (20.31±0.20)×${10}^{-3\mathrm{}}$ sec; the 472-kev level of ${\mathrm{Na}}^{24}$, (19.9±0.3)×${10}^{-3\mathrm{}}$ sec; and the 305-kev level of ${\mathrm{As}}^{75}$, (16.8±0.4)×${10}^{-3\mathrm{}}$ sec. The activities were made with a pulsed beam from a Van de Graaff generator. The data were taken with gated radiation-detection circuits in conjunction with a 9-channel time-delay analyzer, and the half-lives were determined by least-squares analysis.

• Received 7 February 1961

DOI:https://doi.org/10.1103/PhysRev.122.1871