Proton branching ratios of Mg 23 levels

Background: The anomalous Ne22 abundance measured in certain presolar graphite grains is thought to arise from the decay of Na22 that was synthesized at high temperatures in core-collapse supernovas. To better interpret this abundance anomaly, the primary destruction mechanism of Na22, the Na22(p,γ)Mg23 reaction, must be better understood. Purpose: Determine proton branching ratios of several Mg23 excited states that play a role in the high-temperature Na22(p,γ)Mg23 reaction rate. Methods: Particle decays of Mg23 excited states populated with the previously reported Mg24(p,d)Mg23 transfer reaction measurement [Kwag, Eur. Phys. J. A 56, 108 (2020)EPJAFV1434-600110.1140/epja/s10050-020-00106-y] 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 Mg24 solid targets. Results: Proton branching ratios of several Mg23 excited states in the energy range Ex=8.044-9.642 MeV were experimentally determined for the first time for the p0 and p1′ (p1+p2+p3) decay channels. Conclusions: These new branching ratios for Mg23 levels can provide an experimental foundation for an improved high-temperature rate of the Na22(p,γ)Mg23 reaction needed to understand production of anomalously high Ne22 abundance in core-collapse supernovas.