Proton branching ratios of Mg23 levels

Abstract

Background: The anomalous $^{22}\mathrm{Ne}$ abundance measured in certain presolar graphite grains is thought to arise from the decay of $^{22}\mathrm{Na}$ that was synthesized at high temperatures in core-collapse supernovas. To better interpret this abundance anomaly, the primary destruction mechanism of $^{22}\mathrm{Na}$, the $^{22}\mathrm{Na}(p,\ensuremath{\gamma})^{23}\mathrm{Mg}$ reaction, must be better understood.Purpose: Determine proton branching ratios of several $^{23}\mathrm{Mg}$ excited states that play a role in the high-temperature $^{22}\mathrm{Na}(p,\ensuremath{\gamma})^{23}\mathrm{Mg}$ reaction rate.Methods: Particle decays of $^{23}\mathrm{Mg}$ excited states populated with the previously reported $^{24}\mathrm{Mg}(p,d)^{23}\mathrm{Mg}$ transfer reaction measurement [Kwag et al., Eur. Phys. J. A 56, 108 (2020)] were analyzed to extract proton branching ratios. The reaction was studied using a 31-MeV proton beam from the Holifield Radioactive Ion Beam Facility of Oak Ridge National Laboratory and $^{24}\mathrm{Mg}$ solid targets.Results: Proton branching ratios of several $^{23}\mathrm{Mg}$ excited states in the energy range ${E}_{x}=8.044\text{\ensuremath{-}}9.642$ MeV were experimentally determined for the first time for the $p0$ and $p{1}^{\ensuremath{'}}$ ($p1+p2+p3$) decay channels.Conclusions: These new branching ratios for $^{23}\mathrm{Mg}$ levels can provide an experimental foundation for an improved high-temperature rate of the $^{22}\mathrm{Na}(p,\ensuremath{\gamma})^{23}\mathrm{Mg}$ reaction needed to understand production of anomalously high $^{22}\mathrm{Ne}$ abundance in core-collapse supernovas.