Resonant scattering of 22Na + p studied by the thick-target inverse-kinematic method.

Background: In presolar low-density graphite grains, an extraordinarily large 22Ne/20Ne ratio or even nearly pure 22Ne is found, pointing to the condensation of radioactive 22Na in grains. Supernovae and neon-rich novae are the main events that produce 22Na via the explosive hydrogen burning process. The 22Na(p, y)23Mg reaction is one of the key reactions that influences the 22Na abundance in ejecta. Purpose: The present work aims to explore the proton resonant states in 23Mg relevant to the astrophysical 22Na(p, γ)23Mg reaction. The determined 23Mg resonant parameters can be used to evaluate the 22Na(p, γ)23Mg reaction rate. Method: A low-energy 22Na radioactive ion beam is produced via the ¹H(22Ne, 22Na)n reaction, and used to measure the experimental excitation function of the 22Na + p resonant scattering with a conventional thick-target inverse kinematic method, R-matrix analysis is applied to deduce the 23Mg resonance parameters from the experimental excitation function. Results: Three proton resonance states in 23Mg are observed. Spins/parities and the proton partial widths are determined. The deduced excitation energies agree with the compiled values. Conclusions: The new spin and parity assignments allow us to perform a shell-model calculation of the γ widths of the 23Mg resonant states for the evaluation of the 22Na(p, γ)23Mg astrophysical reaction rate. The two s-wavc resonant states established in this work at 8.793 and 8.916 MeV in 23Mg, respectively, increase the total reaction rate by about 5% at a temperature greater than 2 GK. [ABSTRACT FROM AUTHOR]