Shape evolution in neutron-rich Zr isotopes through secondary fragmentation reaction

S. Pietri, J. Gerl et al. (GSI Darmstadt),

A. Bruce et al. (Univ. Brighton),

Z. Podolyak et al. (Univ. Surrey),

A. Algora et al. (IFIC Valencia),

D. Sohler et al. (Debrecen)

presented at

AGATA Physics Workshop 2010

Istanbul, Turkey

May 6, 2010

Shape evolution in neutron rich nuclei

How to explain collective phenomena from individual motion?

What are the phases, relevant degrees of freedom, and symmetries of the nuclear many-body system?

Investigate the evolution of shapes and shape changes in nuclei

Neutron-rich medium heavy nuclei are predicted to exhibit dramatic shape effects

Nuclear shapes

phase transitions of the equilibrium shapes

octahedral nuclear shapesrapid shape changes and shape coexistence

Most dramatic shape changes in heavy Zr nuclei

rapid deformation change from

≈ 0.1 to = 0.47

Rapid shape changes in medium heavy nuclei

from spherical via triaxial to prolate deformed

rigid rotor

vibrator

Shape coexistence in heavy Zr nuclei?

Hartree-Fock Bogolyubov

9/2-[514] 5/2+[420] K = 5- ~100 ns isomer

PES for 106Zr: triaxiality

Alignment of g9/2 protons and h11/2 neutrons produce oblate structure

Liquid drop with shell correction

oblate

prolate

X(5) Critical point nuclei

Interacting Boson Model

X(5) Dynamical symmetry

shape transitional nuclei

unexplored Sr to Mo region

Vibrator X(5) Rotor

Def

orm

atio

n

Shape evolution controversy?

prolate

excit

ed s

tate

s kn

own

no e

xcite

d st

ates

kno

wn prolate oblate shape change

sudden deformation

triaxial shapes

shape coexistence

multi quasi-particle states

dynamical symmetries

... Ideal testing ground for theoretical models

Proposed experiment

Goal: Identify low and medium spin yrast

and near-yrast states in 104-108Zr,

and in surrounding n-rich Sr and Mo isotopes,

and determine lifetimes

Technique: secondary fragmentation, relativistic DSAM

Beam: 238U at 750 AMeV, 4x109/spill → 110Mo at 150 AMeV, 7x102/spill

Set-up: AGATA ( detection) LYCCA (channel identification)

Rates

4+

6+

(8+)

2+50Cr

secondary fragmentation of 55Ni on 9Be at 140 AMeV

DSAM lineshapes

108Zr 106Zr 104Zr 102Zr

ions /spill 0.1 0.4 0.7 1.1

2+ excitation /shift 6x103 1.9x104 3.3x104 5.3x104

2+ -yield /shift 1000 3000 5000 8000

max. spin (>10% of 2+) 4+ 6+ 8+ 10+

An example of Mikes run from the early RISING days without mass selection

112Sn →Au

Relativistic Coulomb excitation / fragmentation

excited nucleus

Coulomb interaction

PrefragmentEquilibrated

nucleus

Zs. Podolyak et al.

148Tb

I = 27+

R = 3.2 (3) %

Fragmentation of 208PbFragmentation of 238U

Isomeric ratios

I R [%]

211Fr 29/2+ 5.7 (2)

212Fr 15- 7.5 (2)

213Fr 29/2+ 12.0 (8)

214Ra 17- 6.8 (2)

215Ra 43/2- 3.1 (6)

High Spin population in massive fragmentation

massive fragm.

I (hbar)10 20 30

Secondary fragmentation of 55Ni on 9Be at 140 MeV/u

Mirror symmetry at N Z

2+

4+

6+

(8+)

4+

6+

(8+)

2+50Cr

46Ti

NiCoFeMnCr

CaTi

ArS

Si

E

dE

First observation of higher spin states at relativistic energies

extract lifetimes from lineshapes

Mike Bentley et al.