Deformation effects in
185
Au
P. Joshi,
*
A Kumar, and I. M. Govil
Department of Physics, Panjab University, Chandigarh 160014, India
R. P. Singh, G. Mukherjee, S. Muralithar, and R. K. Bhowmik
Nuclear Science Centre, Post Box 10502, New Delhi 110067, India
U. Garg
Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, USA
(Received 12 September 2003; published 2 April 2004)
The nucleus
185
Au was populated using the reaction
159
Tb
30
Si,4n
185
Au at 140 MeV beam energy. Life-
times for the E2 transitions in h
9/2
and i
13/2
bands have been measured using recoil distance method. The
reduced transition probabilities BE2 and transitional quadrupole moments Q
t
were extracted using the mea-
sured lifetimes. Calculations of quasiparticle Routhians and total Routhian surfaces (TRS) have been per-
formed to investigate the effect of the - as well as the -driving properties of these configurations in this
nucleus.
DOI: 10.1103/PhysRevC.69.044304 PACS number(s): 21.10.Tg, 21.10.Ky, 27.70.+q
I. INTRODUCTION
The deformation-driving properties of the high- j intruder
configurations built upon h
9/2
and i
13/2
orbitals have been an
interesting point of investigation in the Z =73–79 and A
=170–180 mass region [1–7]. It is believed that these orbits
belonging to the higher-N shells come down rapidly as a
function of the quadrupole deformation and polarize the
nuclear shape towards large values. Because of their large
slopes on the axis, they do not mix with the other j con-
figurations and hence keep their deformation-driving ten-
dency alive. However, it is still possible for them to mix with
the other K configurations of the same j orbital as a function
of triaxiality . The net deformation-driving tendency
would, therefore, depend upon the slope of the energy of
these orbitals in the - two-dimensional surface. Light
gold nuclei A 185 are good candidates for studying these
effects since their proton Fermi level lies closer to these two
high- j intruder proton configurations, namely h
9/2
5411/2
-
and i
13/2
6601/2
+
. The h
9/2
configuration in these nuclei has
a quasiparticle nature since it lies closer to the Fermi surface
when compared with the i
13/2
configuration which lies above
the Fermi surface and is understood to have the shape polar-
izing tendency. It is, therefore, generally expected that the
band built on the i
13/2
configuration would have a larger
quadrupole deformation compared to the band built on the
h
9/2
configuration. Our previous measurements on
183
Au
nucleus [6] have shown similar deformation-driving effects.
In order to have a more systematic investigation of this effect
in this mass region, we have performed lifetime measure-
ments in the rotational bands built upon h
9/2
and i
13/2
con-
figurations in the
185
Au nucleus.
II. EXPERIMENTAL DETAILS AND DATA ANALYSIS
The reaction
159
Tb
30
Si,4n was used to populate high
spin states in
185
Au. A 140 MeV
30
Si beam was provided by
the 15 UD pelletron accelerator at NSC, New Delhi. The
Gamma Detector Array [8] consisting of 12 Compton sup-
pressed HPGe detectors was used for detecting the rays,
with a 14-element BGO array used as a multiplicity filter.
*Present address: Physics Department, University of York, YO10
5DD, York, UK.
FIG. 1. The shifted (S) and unshifted (U) peaks at various target
to stopper distances for
185
Au nucleus.
PHYSICAL REVIEW C 69, 044304 (2004)
0556-2813/2004/69(4)/044304(5)/$22.50 ©2004 The American Physical Society 69 044304-1