Science and Technology Journal of BgNS, VOL. 13, No. 1, JUNE 2009
ISSN 1310-8727
Title:
EVOLUTION OF THE SHELL STRUCTURE FAR FROM STABILITY
BY MEANS OF HIGH INTENSITY STABLE BEAMS
Authors:
G. de Angelis
Abstract:
The study of nuclear structure far from stability: which mainly on the
availability of radioactive nuclear beams, can complementary be addressed by means of
high intensity beams of stable ions. In particular high intensity beams of stable ions can
open new avenues for the nuclear structure research both for proton and neutron rich
systems. Deep-inelastic and multi nucleon transfer reactions are a powerful tool to
populate yrast and non yrast states in neutron-rich nuclei. Particularly successful is here
the combination of large acceptance spectrometers with highly segmented γ-detector
arrays. Such devices, eventually complemented by large coverage particle detectors can
provide the necessary channel selectivity to identify very rare signals. An example is the
CLARA γ-ray detector array coupled with the PRISMA spectrometer at the Legnaro
National Laboratories (NLN). Large data sets have been recently collected for nuclei close
to the N=28, 40 and 50 shell closures. The obtained results complement studies performed
with current radioactive beam (RIB) facilities. The data clearly show the evolution of the
effective single particle energies in very good agreement with the predictions of the mean
field model with tensor interaction. The excited states of the N=50 isotopes, extended
down to Z=31 and of N=51 isotopes, extended down to Z=34, have been used to test the
predictions of the shell evolution based on the effects of the tensor interaction as well as
of the different effective interaction. As future perspective the development of a γ-ray
detection system capable of tracking the location of the energy deposited at every γ-ray
interaction point will also provide an un parallel level of detection sensitivity, and will
open new revenues for nuclear structure studies.
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