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


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

Datta, U.; Rahaman, A.; Aumann, T.; Beceiro-Novo, S.; Boretzky, K.; Caesar, C.; Carlson, B. V.; Catford, W. N.; Chakraborty, S.; Chartier, M.; Cortina-Gil, D.; de Angelis, G.; Diaz Fernandez, P.; Emling, H.; Ershova, O.; Fraile, L. M.; Geissel, H.; Gonzalez-Diaz, D.; Jonson, B.; Johansson, H.; Kalantar-Nayestanaki, N.; Kröll, T.; Krücken, R.; Kurcewicz, J.; Langer, C.; Le Bleis, T.; Leifels, Y.; Marganiec, J.; Münzenberg, G.; Najafi, M. A.; Nilsson, T.; Nociforo, C.; Panin, V.; Paschalis, S.; Plag, R.; Reifarth, R.; Ricciardi, V.; Rossi, D.; Scheit, H.; Scheidenberger, C.; Simon, H.; Taylor, J. T.; Togano, Y.; Typel, S.; Volkov, V.; Wagner, A.; Wamers, F.; Weick, H.; Weigand, M.; Winfield, J. S.; Yakorev, D.; Zoric, M.

The first direct experimental evidence of a multiparticle-hole ground state configuration of the neutron-rich Mg33 isotope has been obtained via intermediate energy (400 A MeV) Coulomb dissociation measurement. The major part ∼(70±13)% of the cross section is observed to populate the excited states of Mg32 after the Coulomb breakup of Mg33. The shapes of the differential Coulomb dissociation cross sections in coincidence with different core excited states favor that the valence neutron occupies both the s1/2 and p3/2 orbitals. These experimental findings suggest a significant reduction and merging of sd-pf shell gaps at N∼20 and 28. The ground state configuration of Mg33 is predominantly a combination of Mg32(3.0,3.5MeV;2-,1-)νs1/2, Mg32(2.5MeV;2+)νp3/2, and Mg32(0;0+)νp3/2. 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.

Keywords: nuclear physics reaction neutron-rich shell model

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Publ.-Id: 24261