Direct experimental evidence for a multiparticle-hole ground state configuration of deformed Mg-33

©2016 American Physical Society. Articulo firmado por más de 10 autores. The authors wish to thank the accelerator staff of GSI for their active support during the experiment. Ushasi Datta acknowledges the Alexander von Humboldt Foundation and SEND project (PIN: 11-R&D-SIN-5.11-0400), Govt. of India, for their support of the experimental investigation and is also grateful to Prof. B. M. Sherrill, NSCL, and Prof. Larry Zamick, Rutgers University, for many valuable suggestions and discussion.
The first direct experimental evidence of a multiparticle-hole ground state configuration of the neutron-rich Mg-33 isotope has been obtained via intermediate energy (400 A MeV) Coulomb dissociation measurement. The major part similar to(70 +/- 13)% of the cross section is observed to populate the excited states of Mg-32 after the Coulomb breakup of Mg-33. The shapes of the differential Coulomb dissociation cross sections in coincidence with different core excited states favor that the valence neutron occupies both the s(1/2) and p(3/2) orbitals. These experimental findings suggest a significant reduction and merging of sd-pf shell gaps at N similar to 20 and 28. The ground state configuration of Mg-33 is predominantly a combination of Mg-32(3.0,3.5MeV; 2(-), 1(-)) circle times nu(s1/2), Mg-32(2.5MeV; 2(+)) circle times nu(p3/2), and Mg-32(0; 0(+)) circle times nu(p3/2). The experimentally obtained quantitative spectroscopic information for the valence neutron occupation of the s and p orbitals, coupled with different core states, is in agreement with Monte Carlo shell model (MCSM) calculation using 3 MeV as the shell gap at N = 20.
Alexander von Humboldt Foundation
SEND project, Govt. of India
Depto. de Estructura de la Materia, Física Térmica y Electrónica
Fac. de Ciencias Físicas
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