Lifetime of the 6.14-Mev3−State ofO16by a Recoil Method

Abstract

The lifetime of the 6.14-Mev $3^{-}$ state of ${\mathrm{O}}^{16}$ has been measured by means of a recoil technique. The spatial distribution of decays of recoiling ${\mathrm{O}}^{16}$ nuclei, produced by the reaction ${\mathrm{F}}^{19}(p, {\alpha }_1){\mathrm{O}}^{16*}$, was studied with a highly collimated $\gamma$-ray detector. Comparison with the corresponding distribution obtained when the ${\mathrm{O}}^{16}$ nuclei were stopped at the target surface by an evaporated metallic layer provided a means of determining the lifetime. A value for this half-life of (8.6±4.0)×${10}^{-12\mathrm{}}$ second [mean life, $\tau =(1.2\mathrm{}\pm 0.6)\times {10}^{-11\mathrm{}}$ sec] has been found, consistent with previously established limits. The measured value is compared with values predicted from various nuclear models.