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

TL;DR

This study measures the radiative width of the Hoyle state in carbon-12 using gamma-ray spectroscopy, providing a more accurate value that influences stellar evolution and nucleosynthesis models.

Contribution

The paper presents a new measurement of the Hoyle state's radiative width, which is approximately 34% higher than previous estimates, refining key nuclear data.

Findings

Radiative width of the Hoyle state is determined as 5.1(6) x 10^{-3} eV.

The measured radiative branching ratio is 6.2(6) x 10^{-4}.

Results suggest revisions to models of stellar evolution.

Abstract

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. C 102, 024320 and the currently adopted $\Gamma_{\pi}(E0)$ values, the radiative width of the Hoyle state is determined as $\Gamma_{\rm rad}=5.1(6) \times 10^{-3}$ eV. This value is about 34% higher than the currently adopted value and will impact on models of stellar evolution and nucleosynthesis.