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HK: Hadronen und Kerne
HK 50: Spectroscopy: 130 ≤ A ≤ 180
HK 50.8: Group Report
Wednesday, March 18, 1998, 16:15–16:45, D
New insights in the first backbending region of heavy Dy-isotopes⋆ — •T. Härtlein1, H. Bauer1, B. Binder1, A. Dietrich1, Ch. Gund1, D. Pansegrau1, D. Schwalm1, A. Jungclaus2, G. Hagemann3, D. Napoli4, S. Lunardi4, G. de Angelis4, C. Ur4, and A. Gadea4 — 1MPI für Kernphysik Heidelberg — 2Uni Göttingen — 3NBI Kopenhagen — 4INFN Legnaro
The interpretation of the first backbend in deformed
rare earth nuclei as a crossing of the ground state band with
a rotational band built on an aligned i13/2 neutron pair
is rather well established.
Especially in the light neutron deficient
nuclei, this picture is rather
successful and the crossing frequency as well as the oscillating
behaviour of the interaction strength when filling the i13/2
neutron shell is readily understood
in the framework of
cranked shell model [1].
However, in more neutron rich nuclei like 160/162Dy,
some additional aspects occour, which do cannot be explained
in the usual picture.
For example
in 162Dy, the crossing frequency of the first backbend is shifted upwards
by 50 keV to
ℏ ωc ≈ 320 keV what is an unexpected behaviour for a nucleus
in that mass region.
Furthermore, in Coulomb excitation of 160Dy, an exclusive population
of yrast states in and above the backbending region is observed, which cannot
be explaind in terms of a two band mixing model [2].
Therefore two complementary types of experiments were performed during the german
CLUSTER campaign and at GASP,
to get detailed
and more complete
information about the nuclear structure in the
region of the first backbend.
Using the incomplete fusion reaction
158/160Gd(7Li,xn and pxn),
it was possible for the first time to populate the rather n-rich nuclei
159−162Ho and 160−163Dy with
angular momentum up to
28ℏ and thereby to
extend our knowledge about the i13/2-qp band and
further interacting bands over a wide range.
Using Coulomb excitation, which is a coherent and diabatic process,
additional information about the wave functions of the interesting states
and the phases of the connecting matrix elements could be obtained.
⋆ supported by BMBF
[1] G. B. Hagemann, I. Hamamoto, Phys. Rev. C46, 838 (1992)
[2] T. Härtlein et al., Prog. Part. Nucl. Phys. 38, 309 (1997)