Transitions in Nuclear Structure of Heavy,

1
Transitions in Nuclear Structure of Heavy,
Neutron-Rich Nuclei Structural Evolution from
170Dy to 208Pb
Paddy Regan Dept,. Of Physics University of
Surrey, Guildford, UK p.regan_at_surrey.ac.uk
2
Outline

• The valence maximum..approaching 170Dy104
• The magical journey south at N126
• Somewhere in the middle.the A190 W,Os
  spectroscopy with RISING

3
(No Transcript)
4
R(E(4) / E(2)) Systematics plot from Burcu
Cakirli
5
170Dy

• Np.Nn max. nucleus (below 208Pb anyway)max
  collectivityshould be one of the best cases of
  an axially symmetric, quadrupole deformed
  nucleus.
• Neutron-rich, cant get to with
  fusion-evaporation.
• Can make with DIC at Coulomb barrier energiesif
  we know something to start with

6
(No Transcript)
7
P.A. Soderstroem, J. Nyberg, P.H. Regan et al.,
CLARA PRISMA Data,

• 82Se beam on a 170Er target Total Z34 68
  102 A 170 82 252
• Eb20 above Coulomb barrier for DIC
• Use PRISMA spectrometer to define direction and
  nature of (lighter) BLFs.
• Assume simple 2-body (elastic) kinematics for
  Doppler corrections
• Assume no proton evaporation from (neutron-rich)
  residues.
• Seems to work (with typically 0n ? 6n neutron
  total evaporation)

8
(No Transcript)
9
First Evidence for (the 4 ? 2 in) 170Dy ?
4 ?2 in 170Dy ?
Gated on BLF Eg777 keV 2 ?0 in 82Kr show
coincs for Doppler corrected 170-nDy TLFs
10
Most nuclei are radioactive. How do you make
them and study them ?
11
Accelerator facility at GSI-Darmstadt

• The Accelerators
• UNILAC (injector) E11.4 MeV/n
• SIS 18Tm corr. U 1 GeV/n
• Beam Currents
• 238U - 108 pps
• some medium mass nuclei- 109 pps
• (A130)

• FRS provides secondary radioactive ion beams
• fragmentation or fission of primary beams
• high secondary beam energies 100 700 MeV/u
• fully stripped ions

12
Ion-by-ion identification with the FRS
TOF
?E
Cocktail of secondary, exotic fragments with
x00 MeV/u thru. FRS. Separate and identify
event-by-event. Chemically independent.
13
see S. Pietri et al., Nucl. Inst. Meth. Phys.
Res. B261 (2007) 1079
14
(No Transcript)
15
(No Transcript)
16
Passive stopper For isomeric decays, T1/2lt 1 ms
17
see S. Pietri et al., Nucl. Inst. Meth. Phys.
Res. B261 (2007) 1079
18
Information gathered from Passive Stopper RISING
Stopped Beam (A200)
205Au
S.J. Steer et al., IJMP E18 (2009) 1002
204Pt
?
N126
19
(No Transcript)
20
Aside interest.is there N126 shell quenching ?
r-process abundances
mass number A
Assumption of a N126 shell quenching leads to a
considerable improvement in the global abundance
fit in r-process calculations
21
(No Transcript)
22
S.J. Steer, Zs. Podolyak et al., Int. Jour.
Mod. Phys. E18 (2009) 1002
23
(No Transcript)
24
(No Transcript)
25
Probing deeper into the N126 shell closure
First structural information on 203Ir (Z77,
N126)
S.J. Steer et al., Int. Jour. Mod. Phys. E18
(2009) 1002
26
The Principle of the Active Stopper
Focal plane implantation detector sensitive to
electron emission
Si Strips
The waiting time between particle implantation
and b-particle (or i.c. electron) emission is a
measure of the decay half-life. Gamma rays
emitted following these decays are detected by
the RISING array.
27
RISING Active Stopper Measurements
Passive Stopper g ray from isomer cascades with
T1/2 10 ns ? 1 ms.
Active Stopper measurements b-particles,
internal conversion electrons. T1/2 up to
minutes associated with delayed g-rays.
5 cm x 5 cm DSSSD (16 strips x 16 strips 256
pixels) x 3 758 total pixels.
See P.H. Regan, N. Alkhomashi et al., Int. Jour.
Mod. Phys. E17 (2008) 8 R. Kumar NIM
A598 (2009) 754
28
log. pre-amp to measure electrons (0.1 MeV)
heavy ions (GeV) in same detector.
29
(No Transcript)
30
Passive Stopper measurements g-rays from isomer
with T1/2 for 10 ns ? 1 ms. Active Stopper
measurements b -particles, i.c. electrons, T1/2
ms ?mins
31
Podolyak, Farrelly, Regan et al., Phys. Lett.
B672 (2009) 116
32
194Os.not quite oblate deformed 192Os (N116)
lowest 22 in Os chain (see Nasser talk next re
190W) What about heavier Os as the N126 is
approached ?
33
194Re ?194Os b- Decay with RISING Active Stopper
Confirmation of low-spin decay scheme for 194Os
(N. Al-Dahan et al.,)
34
(No Transcript)
35
All newopening up the neutron-rich by
fragmentation isomer spectroscopy of 208Pb Can we
get to Osmium (202) next N126 ?
S.J. Steer PhD thesis, University of Surrey
(2008)
36
(No Transcript)
37

• Summary
• Approaching 170Dy using DICs best rotors ?
• Deep proton-hole excitations in N126 (RISING)
  from
• Isomer spectroscopy (205Au, 204Pt, 203Ir) and
• Internal conversion spectroscopy (205Au)
• Prolate - oblate spherical transitions through
  the Tungsten and
• Osmium isotopes.
• Future
• More RISING followed by PRESPEC to see more
  N126 N82 isomers
• Then DESPEC project at FAIR.
• More DIC at Legnaro using AGATA demonstrator.

38
If you think this is coolwe have a PDRA job
open