Structure of 23Al from the one-proton breakup reaction and astrophysical implications

The ground state of the proton-rich nucleus 23Al has been studied by one-proton removal on a carbon target at about 50Â MeV/nucleon using the EXOGAM + SPEG experimental setup at GANIL. Longitudinal momentum distributions of the 22Mg breakup fragments, inclusive and in coincidence with γ rays de-exciting the residues, were measured. The ground-state structure of 23Al is found to be a configuration mixing of a d-orbital valence proton coupled to four core states-0gs+, 21+, 41+, 42+. We confirm the ground state spin and parity of 23Al as Jπ=5/2⁺. The measured exclusive momentum distributions are compared with extended Glauber model calculations to extract spectroscopic factors and asymptotic normalization coefficients (ANCs). The spectroscopic factors are presented in comparison with those obtained from large-scale shell model calculations. We determined the asymptotic normalization coefficient of the nuclear system 23Al_gs → 22Mg(0⁺) + p to be Cd_5/22⁽23Al_gs)=(3.90±0.44) ×103fm^-1, and used it to infer the stellar reaction rate of the direct radiative proton capture 22Mg(p,γ)23Al. Astrophysical implications related to 22Na nucleosynthesis in ONe novae and the use of one-nucleon breakup at intermediate energies as an indirect method in nuclear astrophysics are discussed.