We report on the first in-beam γ-ray spectroscopy of \nuc{23}{Al} using two different reactions at intermediate beam energies: inelastic scattering off \nuc{9}{Be} and heavy-ion induced one-proton pickup, \nuc{9}{Be}(\nuc{22}{Mg},\nuc{23}{Al}+γ)X, at 75.1 MeV/nucleon. A γ-ray transition at 1616(8) keV -- exceeding the proton separation energy by 1494 keV -- was observed in both reactions. From shell model and proton decay calculations we argue that this γ-ray decay proceeds from the core-excited 7/2+ state to the 5/2+ ground state of \nuc{23}{Al}. The proposed nature of this state, [\nuc22Mg(21+)⊗πd5/2]7/2+, is consistent with the presence of a gamma-branch and with the population of this state in the two reactions.
@article{arxiv.0807.2293,
title = {In-beam gamma-ray spectroscopy at the proton dripline: 23Al},
author = {A. Gade and P. Adrich and D. Bazin and M. D. Bowen and B. A. Brown and C. M. Campbell and J. M. Cook and T. Glasmacher and K. Hosier and S. McDaniel and D. McGlinchery and A. Obertelli and L. A. Riley and K. Siwek and J. A. Tostevin and D. Weisshaar},
journal= {arXiv preprint arXiv:0807.2293},
year = {2009}
}