Science and Technology Journal of BgNS, VOL. 13, No. 1, JUNE

Science and Technology Journal of BgNS, VOL. 13, No. 1, JUNE 2009
ISSN 1310-8727
Nuclei are complex quantum many-body systems, composed of two kinds of
interacting. Yet, they display amazing simplicities and regularities. Nuclei with sufficient
numbers of protons and neutrons exhibit collective phenomena where the structure arises
from the coherent motion of the nucleons and the nucleus can be modeled semi-classically
as a liquid drop. Recently, the concept of quantum phase transitions has been applied to
equilibrium shape changes in atomic nuclei and newly proposed critical point symmetries
(CPS) can now describe nuclei at the point of a phase transition from spherical to
deformed shapes. Any successful model soon generates modifications and also often
spawns new models.The rapidly advancing area of new modifications to the CPS will be
discussed, which now provides analytic solutions to describe a wider range of structures
between spherical and deformed shapes. To test the X(5) critical point symmetry in a
previously unexplored region, an experiment on 130Ce was performed. TheLow-lying
states of 130Ce are compared to the X(5) critical point model as wqll as to a newer
extension, the
model. To explore to what extent new modifications to the CPS
describe the properties of actual nuclei, an experiment on 168Hf was performed. The data
on 168Hf are compared with some new geometrical model predictions.
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