Ground-state configuration of neutron-rich ~(35)Al via Coulomb breakup

摘要

The ground-state configuration of ~(35)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 ~(35)Al, integrated up to 5.0 MeV relative energy between the ~(34)Al core and the neutron using a Pb target, is 78(13) mb. The exclusive measured CD cross section that populates various excited states of ~(34)Al is 29(7) mb. The differential CD cross section of ~(35)Al → ~(34)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 ~(35)Al could be, tentatively, 1/2~+ or 3/2~+ or 5/2~+. The valence neutrons, in the ground state of ~(35)Al, may occupy a combination of either l = 3,0 or l = 1,2 orbitals coupled with the ~(34)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 ~(35)Al as suggested in the literature, then the major ground-state configuration of ~(35)Al is a combination of ~(34)Al(g.s.; 4~-) ? ν_(p3/2) and ~(34)Al(isomer; 1~+) ? ν_(d3/2) states. The result from this experiment has been compared with that from a previous knockout measurement and a calculation using the SDPF-M interaction.