Examining the exotic structure of the proton-rich nucleus Al23

The longitudinal momentum distribution (P//) of fragments after one-proton removal from Al23 and reaction cross sections (σR) for Al23,24 on a carbon target at 74A MeV have been measured. The Al23,24 ions were produced through projectile fragmentation of 135A MeV Si28 primary beam using the RIPS fragment separator at RIKEN. P// is measured by a direct time-of-flight (TOF) technique, while σR is determined using a transmission method. An enhancement in σR is observed for Al23 compared with Al24. The P// for Mg22 fragments from Al23 breakup has been obtained for the first time. FWHM of the distributions has been determined to be 232 ± 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 Al23, indicating that Al23 is not a proton halo nucleus.