Spin assignments for Mg-23 levels and the astrophysical Na-22(p, gamma)Mg-23 reaction

Abstract

The 22Na(p)23Mg reaction is responsible for destruction of the long-lived radionuclide 22Naproduced during nova explosions. Since the reaction proceeds through resonances from levels in 23Mg above the proton threshold at 7.581 MeV, the properties of these levels such as excitation energies, spins, and parities are crucial ingredients to determine the 22Na(p,.)23Mg reaction rate. Despite recent studies of these levels, their spins are not well constrained in many cases. We have measured the 24Mg(p, d)23Mg transfer reaction to determine spectroscopic properties of these levels at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. The spin of the Ex = 7.788 MeV level in 23Mg is constrained to be J p = (3/2+, 5/2+) through the present work. The astrophysical 22Na(p,.)23Mg reaction rate at nova temperatures is updated accordingly. Nova nucleosynthesis model calculations using the newly updated 22Na(p,.)23Mg reaction rate shows that the final weighted abundance of the radionuclide 22Nais increased by42% compared to that obtained by using the previous 22Na(p)23Mg reaction rate of Sallaska et al. for a 1.35 M ONeMg white dwarf.