Examining the exotic structure of the proton-rich nucleusAl23

Abstract

The longitudinal momentum distribution (${P}_{//}$) of fragments after one-proton removal from $^{23}\mathrm{Al}$ and reaction cross sections (${\ensuremath{\sigma}}_{R}$) for $^{23,24}\mathrm{Al}$ on a carbon target at $74A$ MeV have been measured. The $^{23,24}\mathrm{Al}$ ions were produced through projectile fragmentation of $135A$ MeV $^{28}\mathrm{Si}$ primary beam using the RIPS fragment separator at RIKEN. ${P}_{//}$ is measured by a direct time-of-flight (TOF) technique, while ${\ensuremath{\sigma}}_{R}$ is determined using a transmission method. An enhancement in ${\ensuremath{\sigma}}_{R}$ is observed for $^{23}\mathrm{Al}$ compared with $^{24}\mathrm{Al}$. The ${P}_{//}$ for $^{22}\mathrm{Mg}$ fragments from $^{23}\mathrm{Al}$ breakup has been obtained for the first time. FWHM of the distributions has been determined to be 232 \ifmmode\pm\else\textpm\fi{} 28 MeV/$c$. The experimental data are discussed by using the Few-Body Glauber model. Analysis of ${P}_{//}$ demonstrates a dominant $d$-wave configuration for the valence proton in ground state of $^{23}\mathrm{Al}$, indicating that $^{23}\mathrm{Al}$ is not a proton halo nucleus.