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HEIDI WATKINS
2009 IoP NUCLEAR PHYSICS CONFERENCE
UNIVERSITY OF BIRMINGHAM
Plunger Measurements of
Shape Coexistence in the
Neutron Deficient 174Pt Nuclei
OVERVIEW
Physics Motivation.
Shape Coexistence approaching Z = 82 shell gap.
Experimental Techniques.
Recoil distance Doppler-shift lifetime measurements (RDDS).
Status of Analysis.
Lifetime Analysis of 174Pt.
SHAPE COEXISTENCE
A phenomenon where nuclear configurations at similar excitation energies are
built on very different deformations.
Shape coexistence is expected to occur in transitional regions between
weakly and strongly deformed ground states.
E (
ħ
)
2
GROUND STATE
(Weakly Deformed)
EXCITED
(Well Deformed)
PROLATEOBLATESPHERICAL
A. Andreyev et al. Nature 405 (2000) 430
0p-0h 2p-2h 4p-4h
SHAPE COEXISTENCE NEAR THE Z=82 SHELL CLOSURE
The three different shapes
are observed in three
separate bands in 186Pb.
SHAPE COEXISTENCE NEAR THE Z=82 SHELL CLOSURE
Shape coexistence observed in 174Pt is
a result of band crossing between two
minima.
The deformation can be inferred from
the experimental measurement of the
lifetime of the state.
The amount of mixing between these
shapes can be determined by the
reduced transition probabilities.
2)2( tQEB GD Dracoulis et al. Phys. Rev. C 44, R1246 (1991)
21tQ
EXPERIMENTAL TECHNIQUE – FAR FROM STABILITY
The Segre Chart of Nuclides
Region of Interest
EXPERIMENTAL TECHNIQUES – FUSION EVAPORATION
86Sr16+ + 1mgcm-2 92Mo @ 401MeV
GREATFocal Plane
Spectrometer
RITUGas Filled Recoil
Separator
JUROGAM (Phase II)15 Ge +
12 Clover detectors
EXPERIMENTAL TECHNIQUES - RDT
a
Pixels of the DSSD
EXPERIMENTAL TECHNIQUES - RDDS
Plunger is specifically
developed by the
University of Koln to
utilise the RDT technique.
The device is coupled
to Jurogam + RITU.
1 mgcm-2 Mg degrader
foil.
EXPERIMENTAL TECHNIQUES - RDDS
Beam current IB ~ 2pnA.
RITU transmission
decreased by 2/3.
Dv/c is small 1.1%
4.4% 3.3%.
Detector angles
5 @ 158o
10 @ 134o
cos10
c
vEE
CURRENT ANALYSIS – 174Pt
Fully Doppler-shifted 174Pt g-ray
spectra from the plunger data. J TM Goon et al., Phys. Rev. C 70, 014309 (2004)
Energy / keV
Co
un
ts
174Pt Alpha Tagged Jurogam Spectra
394
497 & 501
461
474
477 keV
474 keV
465 keV
462 keV
LIFETIME MEASUREMENT OF THE 6+ STATEA measurement for the lifetime of the 6+ state of 174Pt:
2.2 (8) ps.
This lifetime corresponds to a quadrupole
moment of:
|Q| = 7 (2) eb.
A deformation parameter of:
b2 = 0.27 (7).
A reduced transition probability of:
B(E2) = 1.5 (9) (eb)2.
The analysis of these measurements is on going.
TRS calculations predict a very g-soft gs with
b2 ~0.13 and a shape change to b2 ~ 0.21
GD Dracoulis et al.
CONCLUSION / OUTLOOK
Extract the quadrupole moments of the oblate
and prolate configurations of 175Au.
Also to compare the relative deformations of
175Au and 174Pt to investigate the core-polarising
properties of single-proton states.
COLLABORATORST. Grahn, D.T Joss, L Bianco, P.A Butler, R Carroll, R.D Herzberg, J Pakarinen, R.D Page,
E.S Paul, A Petts, J Revill, S Rigby, P.J Sapple, M Scheck, J Thomson.
T Back, B Cederwall, M Sandzelius.
I.G Darby.
A Dewald, C Fransen, M Hackstein, T Munchen, T Pissalla, W Rothen.
T Faestermann, R Gernhauser, T Kroll, R Krucken, P Maierbeck.
P.T Greenless, U Jacobsson, P.M Jones, R Julin, S Juutinen, S Ketelhut, M Leino,
M Nyman, P Nieminen, P Peura, P Rahkila, P Ruotsalainen, J Saren, C Scholey, J Sorri,
J Uusitalo.
D O’Donnell, M Labiche, J Simpson.
O Moller.
N Lumley.
SHAPE COEXISTENCE NEAR THE Z=82 SHELL CLOSURE
The nuclei 175Au provide a
unique opportunity to
investigate the shape driving
properties of proton
excitations.
The deformation can be
inferred from the experimental
measurement of the lifetime of
the state.
21tQ
FG Kondev et al., Phys. Lett. B512 (2001) 268
CURRENT ANALYSIS – 175Au
D O’Donnell et al performed a Fusion Evaporation Reaction
92Mo(84Sr,p2n)175Au* @ 403MeV at JYFL.
Additional bands observed as a result of the orbital of the unpaired proton.
175Au
EXPERIMENTAL TECHNIQUES - DDCM
Lifetimes are derived using the Differential Decay Curve Method – DDCM.
Where is the area of the Doppler shifted component and is the area of the degraded component of the g-ray peaks corresponding to the transition Li Lj.
Also bij is the branching ration of the transition i j and Jhi and Jij are the relative intensities of the g-ray transitions.
dtddQ
dQJJbdQd
ij
h hiijhiijij
i/)(
)(/)()(
)()(
)(
)(
)()(
dIdI
dI
OR
dRdQ
d
ij
s
ij
d
ij
ij
ij
ij
s
ijI
d
ijI
EXPERIMENTAL TECHNIQUES - DDCM
The resulting lifetime is a weighted average of the values (d) corresponding to the different target-to-distance distances d.
The values of (d) determined inside the region of sensitivity should be constant.
Only direct feeding transitions to the level of interest have to be considered.
Errors of the lifetimes are determined by the statistical errors Intensities of the degraded and full Doppler-shifted components
of g-rays
The error introduced determining the derivative of the decay curve.