Resumen:
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The ground-state configuration of ³?Al has been studied via Coulomb dissociation (CD) using the LAND-FRS setup (GSI, Darmstadt) at a relativistic energy of ~ 403 MeV/nucleon. The measured inclusive differential CD cross section for ³?Al, integrated up to 5.0 MeV relative energy between the ³³Al core and the neutron using a Pb target, is 78(13) mb. The exclusive measured CD cross section that populates various excited states of ³³Al is 29(7) mb. The differential CD cross section of ³?Al -> ³?Al + n has been interpreted in the light of a direct breakup model, and it suggests that the possible ground-state spin and parity of ³?Al could be, tentatively, 1/2? or 3/2? or 5/2?. The valence neutrons, in the ground state of ³?Al, may occupy a combination of either l = 3,0 or l = 1,2 orbitals coupled with the ³?Al core in the ground and isomeric state(s), respectively. This hints of a particle-hole configuration of the neutron across the magic shell gaps at N = 20,28 which suggests narrowing the magic shell gap. If the 5/2? is the ground-state spin-parity of ³?Al as suggested in the literature, then the major ground-state configuration of ³?Al is a combination of ³?Al (g. s.; 4?) circle times ?_(p_(3/2)) and ³?Al (isomer; 1?) circle times ? _(d_(3/2)) states. The result from this experiment has been compared with that from a previous knockout measurement and a calculation using the SDPF-M interaction.
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