Lifetime of the First Excited State ofC15

The lifetime of the first excited state of ${\mathrm{C}}^{15}$(0.750 MeV, ${\frac{5}{2}}^{+}$) produced in the ${\mathrm{Be}}^9({\mathrm{Li}}^7, p){\mathrm{C}}^{15}$ reaction was measured using the delayed-coincidence technique. A solid-state detector was used to measure the energies of the protons as well as to produce timing signals. The mean lifetime was determined to be (3.77±0.11)×${10}^{-9\mathrm{}}$ sec. This result is in good agreement with an earlier value of (3.73±0.23)×${10}^{-9\mathrm{}}$ sec obtained using a pulsed-beam method. Disagreement with weak-coupling collective-model predictions based on neighboring $2s_{\frac{1}{2}}\to 1d_{\frac{5}{2}}$ transitions is thus not removed.