By using a large-acceptance position-sensitive silicon detector array in coincidence with the high-resolution Munich Q3D spectrograph, unambiguous measurements have been made of the absolute $\alpha$-particle decay widths from excited states in ${}^{16}\mathrm{O}$* in the energy range 13.85 to 15.87 MeV. Carbon targets have been bombarded with 42-MeV ${}^6\mathrm{Li}$ beams to induce ${}_{\hspace{0.5em}6}^{12}$C(${}_3^6$Li, $d$)${}_{\hspace{0.5em}8}^{16}$O* reactions. The deuteron ejectiles were measured in the Q3D and the results gated by ${}^4\mathrm{He}+{}^{12}\mathrm{C}$ breakup products detected in the silicon array, the efficiency of which was modeled using Monte Carlo simulations. By comparing total population and breakup-gated spectra, the following absolute $\alpha$-decay widths have been measured with high resolution: ${\Gamma }_{\alpha 0}/{\Gamma }_{\text{tot}}$ $=\hspace{0.5em}0.87\pm 0.11$ (13.980 MeV), $1.04\pm 0.15$ (14.302 MeV), $0.92\pm 0.10$ (14.399 MeV), $0.59\pm 0.04$ (14.815 MeV), $0.88\pm 0.18$ (15.785 MeV), and ${\Gamma }_{\alpha 1}/{\Gamma }_{\text{tot}}=1.14\pm 0.08$ (14.660 MeV), $0.46\pm 0.06$ (14.815 MeV).

• Received 18 March 2011

DOI:https://doi.org/10.1103/PhysRevC.83.064324