Decay studies in Exotic, Neutron-Rich A~200 Nuclei

Steven Steer for the Stopped Beam RISING Collaboration

Dept. of Physics, University of SurreyGuildford, Surrey, GU2 7XH, UK

s.steer@surrey.ac.uk

The RISING ‘Stopped Beam’ Campaign

Passive Stopper :

Isomer (gamma) decay Measurements

Active Stopper :

Isomer internal conversion electron and beta-decay

measurements

Today three experiments will be discussed.

All three experiments focus on: Neutron-Rich, Z<82, A~200 nuclei

Fragmentation of 208Pb and 238U

This work is performed at GSI using the Fragment Separator and the RISING gamma-ray spectrometer

Overview of Experiment #1

Fragmentation of E/A = 1GeV 208Pb with passive stopper (isomer gamma decay)

>>

N = 126

Z = 82 >>

The first experimental information on excited states in 15 nuclides.

Previous Kowledge at N=126, Z<82

Z=80

PRL B. Fornal et. al. (2001)

Z=81

Progress at N=126 : Z=77, 203Ir and Z=78 204Pt

Data from 8,000 203Ir nuclei

203Ir

204Pt

Shell-model calculations (M.Górska, H.Grawe, H. Maier, A.Brown)

(a)and (d):TBME from L.Rydstrom et al, NPA512(1990)217 (based on Kuo-Brown interaction)

(b) and (c): three TBMEs modified

Δ(d3/2 h11/2; d3/2 h11/2)7- = +135 keV

Δ(s1/2 d5/2; s1/2 d5/2)2+,3+ =+250 keV (monopole only)

Δ(d3/2 h11/2; s1/2 h11/2)6- changed to +0.160 MeV (fit for B(E2)

Good description of energies and B(EL)s

S.Steer et al., submitted to rapid Communications

Progress at N=126 : Z=79, 205Au

Isomer gamma decay

Isomer conversion electrons

Electron conversion data: Zs. Podolyák et al., submitted to Phys. Lett. B

B(E2; 34) = 1.1 W.u.

B(E3; 962) = 0.4 W.u.

(a) TBME from L.Rydstrom et al, NPA512(1990)217 (based on Kuo-Brown)

(b) Modified (a) to get better desription of 204Pt

203Ir

N=126, Z<82, odd-Z decay schemes

Z=81Z=79Z=77

188Ta → 188W

190Ta → 190W

192Ta → 192W

N. Alkhomashi, P.H. Regan et al.,

Experiment #2: beta decay studies

N=82

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Larger differences at N=126(lack of experimental data)

N=126

N=126 towards r-process path

N. Aldahan, Zs. Podolyak et al.

T1/2 ~ 10 - 100 ns

208Hg (Z=80;N=128)

preliminary

Experiment #3: N>126

The RISING Collaborators

Named collaborators are for the 204Pt

research

In SummaryAnalysis beginning: Beta- and isomer-decay studies

208Hg

Experiment #2

Experiment #3

Experiment #1

27 isomers discovered

48 measured in total

Analysis in progress: Beta-decay studies

188,190,192W

N=122 isotones

S.Yates et al., PRC37 (1988)1889.

πh11/2-1d3/2

πh11/2-1s1/2

From RISING