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2._THE. IMPACT ON THE PHYSICS----
The high resolving power provided by the GAMMASPHERE will open up new
scientific- opportunities- for a broad range of nuclear studies. In the
following we will present a few examples which have been discussed in the
GAMMASPHERE proposal2 and in the talks presented in this conference to
demonstrate the capabilities of GAMMASPHERE.
2.1. Super and hyperdeformed stat-s'^-
High-spin states corresponding to a superdeformed nucleus were found for
the first time in 1986. A rotational band of very large moment of inertia and
deformation was discovered in 152Dy in the I = 22 to 60 range. This dis-
covery has opened a new direction in nuclear physics and subsequently, many
other cases of superdeformation have been observed in the A - 130, 150, and
190 regions. These nuclei have an axially symmetric, prolate spheriodal
shape and the principal axes have a ratio of lengths significantly larger
than the "usual" 1.3 to 1. Like the usual deformed nuclei, they exist
because shell effects provide extra stability for these shapes.
The observation and study of such highly deformed nuclei will give
us a chance to explore new phenomena and ideas: (i) The particular grouping
of the single particle levels which leads to the prediction of regions of
superdeformed nuclei is more generally related3 to special approximate sym-
metries (called pseudo-spin and pseudo-SU(3) symmetries) of the Hamiltonian.
These can be studied by testing the location and strength of shell effects at
large deformation. (ii) We will also have a first look at nuclei where the
ratio of Coulomb to surface energy is significantly different from those we
know. This means that the basic elements determining nuclear structure have a
different relationship to each other. (iii) A truly new phenomenon which
should be accessible with GAMMASPHERE will be the population of theoretically
predicted "hyperdeformed" nuclei, represented by the 3:1 axis ratio shown sche-
matically in Fig. 1. Indeed, such a "hyperdeformed" shape has been reported4
at low spins in 231Th, and possibly in molecular resonances in light nuclei.
The orbitals occupied in these hyperdeformed states originate in very high
shells whose position is quite uncertain. Therefore, experimental information
on hyperdeformed states should provide important constraints to test theoret-
ical models under quite unusual conditions.
The superdeformed states at high spins are hard to find. As shown in
-Fig. 2, the average intensity of these transitions is about 1-2%, and the con--
: Jnection to the low-lying normally deformed states is not known. Here, the
higher-fold coincidences will be quite powerful. This was used recently5 to
L -
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Lee, I-Yang. The Gammasphere, article, January 1, 1990; Tennessee. (https://digital.library.unt.edu/ark:/67531/metadc1196485/m1/3/: accessed July 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.