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

TL;DR

This study investigates the structure of the proton-rich nucleus 23Al through one-proton removal reactions, providing insights into its configuration, spectroscopic factors, and implications for astrophysical processes like nucleosynthesis in novae.

Contribution

It offers a detailed experimental analysis of 23Al's ground state structure, confirms its spin-parity, and derives astrophysical reaction rates using novel indirect methods.

Findings

Confirmed 23Al ground state spin and parity as 5/2+

Measured spectroscopic factors and ANCs for 23Al

Inferred stellar reaction rate for 22Mg(p,γ)23Al

Abstract

The ground state of the proton-rich nucleus 23Al has been studied by one-proton removal on a carbon target at about 50 MeV/nucleon using the EXOGAM + SPEG experimental setup at GANIL. Longitudinal momentum distributions of the 22Mg breakup fragments, inclusive and in coincidence with gamma 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 - 0$^{+}_{gs}$, 2$^{+}_{1}$, 4$^{+}_{1}$, 4$^{+}_{2}$. We confirm the ground state spin and parity of 23Al as $J^{\pi} = 5/2^{+}$. 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 $^{23}$Al$_{gs}$ $\rightarrow$ $^{22}$Mg(0$^{+}$) + p to be $C^{2}_{d_{5/2}}$($^{23}Al_{gs}$) = (3.90 $\pm$ 0.44) $\times$ 10$^{3}$ fm$^{-1}$, and used it to infer the stellar reaction rate of the direct radiative proton capture $^{22}$Mg(p,$\gamma$)$^{23}$Al. Astrophysical implications related to $^{22}$Na nucleosynthesis in ONe novae and the use of one-nucleon breakup at intermediate energies as an indirect method in nuclear astrophysics are discussed.