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HK: Fachverband Hadronen und Kerne

HK 6: Nuclear Structure and Dynamics I

HK 6.4: Vortrag

Montag, 16. März 2009, 15:15–15:30, H-ZO 40

Measurement of the one-neutron removal momentum distribution characterizes ²⁴O as a new doubly magic nucleus — •A. Prochazka — GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany — Justus-Liebig-Universität, Gießen, Germany

First results are reported on the momentum distribution after one-neutron removal from ²⁴O at 920 MeV/u. The investigated isotopes were produced by projectile fragmentation of a 1 GeV/u ⁴⁸Ca beam in a beryllium production target placed at the entrance of the FRagment Separator (FRS). They were separated and identified in-flight at the mid-focal plane of the separator, where a carbon reaction target was placed. Due to the high resolution of the FRS, operated in dispersion matched-mode, precise momentum measurements of secondary fragments could be performed. The secondary fragments produced in the C target were detected at the final achromatic focal plane of the FRS thus providing the measurements independently of the large momentum spread of the primary fragments. The ²³O momentum distribution in the projectile rest frame and the one-neutron removal cross section can be well explained by using an eikonal model with a nearly pure 2s_1/2 occupation probability. This large s-wave probability indicates a spherical shell closure at N=16, thereby experimentally confirming earlier suggestions that ²⁴O is a new doubly magic nucleus.