\mbox{Precision Angular Distribution Data for the \boldmath${}^{16}\mathrm{O}(\gamma,\alpha){}^{12}\mathrm{C}$} Reaction in the Region of the \boldmath$1^-$ Resonance at 9.6~MeV

The HI$\gamma$S Optical Time Projection Chamber has been used to measure angular distribtions for the ${}^{16}\mathrm{O}(\gamma,\alpha){}^{12}\mathrm{C}$ reaction at beam energies of 9.4, 9.5, and 9.8~MeV\@. Intense, nearly-mono\-energetic $\gamma$-ray beams produced at the HI$\gamma$S facility were used with a \mbox{N$_2$O} gas target, and the outgoing $\alpha$ particles were detected using an optical time projection chamber. High statistics runs were made and full angular distributions were obtained at all three beam energies. The data are being analyzed in an effort to resolve previous discrepancies between the relative $E1$-$E2$ phase extracted from ${}^{12}\mathrm{C}(\alpha,\gamma){}^{16}\mathrm{O}$ data~[1] and those predicted from elastic $\alpha$-particle scattering on ${}^{12}\mathrm{C}$~[2]\@.\\[4pt] [1] Assun\c{c}\~{a}o~\emph{et al.}, PRC \textbf{73}, 055801 (2006) \\[0pt] [2] Tischhauser~\emph{et al.}, PRC \textbf{79}, 055803 (2009)