Mainz 2012 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 20: Struktur und Dynamik von Kernen

HK 20.8: Vortrag

Dienstag, 20. März 2012, 18:30–18:45, P 4

shell evolution in neutron-rich Al isotopes around N=20 — •chiara nociforo — GSI, Darmstadt, Germany

The structure of nuclei in the region commonly referred as island of inversion has been extensively studied because of the anomalous breakdown of the N = 20 shell closure. Differently than in Ne, Na and Mg isotopes, the experimental two-neutron separation energy of the Al isotopes do not show anomalies and are well reproduced by large scale shell model calculations involving the full sd proton shell and the pf neutron shell as valence space. Recent magnetic moment measurements performed on the ^33,34Al isotopes have shown large discrepancies with shell model predictions, in the sd and sdpf model spaces, implying a possible extension of a deformed region beyond Z = 12. In order to study the evolution of the single particle occupancy in the Al isotopes we have measured the longitudinal momentum distributions of the ^33,34,35Al from one-neutron removal reactions and the corresponding cross sections at the Fragment Separator at GSI. The beam energy was around 900 MeV/u. The momentum distribution analysis has been performed in the eikonal framework. Comparing our results with shell model predictions, the inferred 2s_1/2 neutron occupancy in the ³³Al ground state wave function is 20-40% lower than the predicted one. The inclusive data do not exclude the presence of intruder states. Some intruder l=1 occupancy is found in ³⁴Al although it is smaller than in ³³Mg.