Angular Correlations in theLi7(p,γ)Be8* (16.63 MeV)→2αReaction

Angular correlations between the $\gamma$ ray populating the 16.63-MeV state of ${\mathrm{Be}}^8$ and the subsequent breakup $\alpha$ particles have been measured at the 0.441-MeV resonance of the ${\mathrm{Li}}^7(p,\gamma ){\mathrm{Be}}^8$ reaction and at an incident proton energy of 1.50 MeV. At the latter energy, the reaction is assumed to proceed by a direct-capture process involving both $S$- and $D$-wave protons. An expression for the $\gamma -\alpha$ angular correlation for a direct-capture reaction is derived, and it compares favorably with the experimental results. The measurement at the 0.441-MeV resonance shows that the 17.64-16.63-MeV $\gamma$-ray transition is nearly pure $M1\mathrm{}$ with a transition amplitude ratio $\delta =\frac{〈E2\mathrm{}〉}{〈M1\mathrm{}〉}=-0.014\mathrm{}\pm 0.013$.