Superdeformed and highly deformed bands in
65
Zn and neutron-proton interactions
in Zn isotopes
C.-H. Yu,
1
C. Baktash,
1
J. Dobaczewski,
2
J. A. Cameron,
3
M. Devlin,
4,
* J. Eberth,
5
A. Galindo-Uribarri,
1
D. S. Haslip,
3,†
D. R. LaFosse,
4,‡
T. J. Lampman,
3
I.-Y. Lee,
6
F. Lerma,
4
A. O. Macchiavelli,
6
S. D. Paul,
1,7
D. C. Radford,
1
D. Rudolph,
8
D. G. Sarantites,
4
C. E. Svensson,
3,6
J. C. Waddington,
3
and J. N. Wilson
5,§
1
Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
2
Institute of Theoretical Physics, Warsaw University, Hoza 69, PL-00681 Warsaw, Poland
3
Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada L8S 4M1
4
Chemistry Department, Washington University, St. Louis, Missouri 63130
5
Institut fu ¨r Kernphysik, Universita ¨t zu Ko ¨ln, D-50937 Ko ¨ln, Germany
6
Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720
7
Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee 37831
8
Department of Physics, Lund University, S-22100 Lund, Sweden
Received 31 May 2000; published 11 September 2000
Superdeformed and highly deformed rotational bands were established in
65
Zn using the
40
Ca(
29
Si,4 p )
65
Zn
reaction, and averaged quadrupole moments were measured for two of these bands. The configurations of these
bands were assigned based on Hartree-Fock calculations. One of the three bands exhibits at low a rise in
the J
(2)
dynamic moments of inertia that is similar to the alignment gain observed in
60
Zn. A comparison of the
rotational band configurations and their J
(2)
moments of inertia for light Zn isotopes suggests that the rise in
J
(2)
is most likely caused by np interactions associated with the valence protons and neutrons occupying the
g
9/2
intruder orbits.
PACS numbers: 21.10.Re, 21.10.Hw, 23.20.Lv, 27.50.+e
Recent studies 1–6 of superdeformed SD and highly
deformed bands in
60-64,68
Zn have allowed systematic
analyses of strongly deformed shapes and configurations in
nuclei with N Z . In the previous study 1 of
60
Zn, a rise in
the J
(2)
moments of inertia of the SD band was interpreted as
the simultaneous alignment of the g
9/2
protons and neutrons.
However, the absence of such an alignment in the SD band
of
61
Zn raises questions 2 of whether or not the T =0 pair-
ing is responsible for such an alignment. To understand the
true cause of the rise in J
(2)
, and to gain insight into the
questions of the possible T =0 pairing, more experimental
data are needed for the neighboring nuclei. In this paper, we
report a study of SD and highly deformed bands in
65
Zn, and
present possible evidence for neutron-proton correlations in
highly-deformed Zn isotopes.
High spin states in
65
Zn were populated using the
40
Ca(
29
Si,4p ) reaction at a beam energy of 130 MeV. The
29
Si beam was provided by the 88-Inch Cyclotron at the
Lawrence Berkeley National Laboratory, and the target con-
sisted of a layer of 0.5 mg/cm
2
enriched
40
Ca evaporated
onto a layer of 2.5 mg/cm
2
Ta foil as backing. The rays
from the reaction were detected by the Gammasphere 7
array, which had 100 detectors at the time of the experiment.
The evaporated charged particles were detected by the 95-
element CsI detector array Microball 8, and the information
obtained was used to select the reaction channel, as well as to
determine the velocity of the recoil for event-by-event Dop-
pler corrections. A total of about 88 million 4-proton gated
or higher fold events were collected from the experi-
ment. Three rotational bands were established from the
reaction-channel-selected cube, and are shown in Fig.
1. Although no connecting transitions were observed be-
tween these bands and the low-spin normally deformed ND
states 9 in
65
Zn, they are assigned to
65
Zn with confidence
due to their unambiguous coincidence relationships with the
known 9 transitions in
65
Zn see Fig. 2.
Among the three established bands, band 1 is the most
strongly populated and is measured to have the largest defor-
mation see ensuing discussions on measurement of Q
t
’s.
The average intensity of this band is approximately 2.5% of
that of the 202-keV ND transition at low spin see Fig. 3.A
spectrum obtained by summing all possible double gates in
this band is strongly in coincidence with the 202-, 864-,
987-, and 1173-keV ND transitions in
65
Zn, as seen in Fig.
2a. For this spectrum, the cube has Doppler correc-
tions performed at two different recoil velocities: For E
1350 keV, v
rec
/ c =0.04, which corresponds to fast decays
of SD bands; for E
1350 keV, v
rec
/ c =0.027, which cor-
responds to decays of low spin states occurring when the
recoil has been slowed down by the backing and is traveling
in vacuum. As a result of this dual-velocity Doppler correc-
tion, Fig. 2a shows narrow peaks for both the SD band as
well as the low spin ND transitions. The spectrum obtained
by summing all possible combinations of double gates on
*Present address: LANSCE-3, MS H855, Los Alamos National
Laboratory, Los Alamos, NM 87545.
†
Present address: Defence Research Establishment Ottawa, Ot-
tawa, Ontario, Canada.
‡
Present address: Department of Physics, State University of New
York at Stony Brook, Stony Brook, NY 11794.
§
Present address: Niels Bohr Institute, Blegdamsvej 17, DK-2100
Copenhagen O ” , Denmark.
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