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.