Structure of the N=50 As, Ge, Ga nuclei

The level structures of the N = 50 As-83, Ge-82, and Ga-81 isotones have been investigated by means of multi-nucleon transfer reactions. A first experiment was performed with the CLARA PRISMA setup to identify these nuclei. A second experiment was carried out with the GASP array in order to deduce the gamma-ray coincidence information. The results obtained on the high-spin states of such nuclei are used to test the stability of the N = 50 shell closure in the region of Ni-78 (Z = 28). The comparison of the experimental level schemes with the shell-model calculations yields an N = 50 energy gap value of 4.7(3) MeV at Z = 28. This value, in a good agreement with the prediction of the finite-range liquid-drop model as well as with the recent large-scale shell model calculations, does not support a weakening of the N = 50 shell gap down to Z = 28. (c) 2012 Elsevier B.V. All rights reserved.

In-beam spectroscopy of Rn-215(86)

The yrast level structure of Rn-215 has been studied by means of in-beam spectroscopy alpha-gamma-gamma coincidence techniques through the Pb-207(O-18,2 alpha 2n) reaction at 93 MeV bombarding energy, using the 8 pi GASP-ISIS spectrometer at Legnaro. New spectroscopic information has been obtained. The deduced low-lying level scheme of Rn-215 does not exhibit the alternating parity structure observed in the heavier known isotones Fr-216, Ra-217, Ac-218, and Th-219. From this result, the lightest nucleus showing evidence for octupole collectivity is Fr-216, defining the lowest-mass corner for this kind of phenomenon as N >= 129 and Z >= 87.