The radiative width of the Hoyle state from $\gamma$-ray spectroscopy

Understand

The cascading 3.21 MeV and 4.44 MeV electric quadrupole transitions have been observed from the Hoyle state at 7.65 MeV excitation energy in $^{12}$C, excited by the $^{12}$C(p,p$^{\prime}$) reaction at 10.7 MeV proton energy.

• From the proton-$\gamma$-$\gamma$ triple coincidence data, a value of ${\Gamma_{\rm rad}}/{\Gamma}=6.2(6) \times 10^{-4}$ was obtained for the radiative branching ratio.
• Using our results, together with ${\Gamma_{\pi}^{E0}}/{\Gamma}$ from Eriksen et al., Phys.
• Rev.