In-beam Spectroscopy of
Transfermium Nuclei
Saclay, 30 January 2007
Rauno Julin
Department of Physics
University of Jyväskylä
Finland
JYFL
Outline:
Introduction
Even-Even
254No
( Z =102, N = 152 )
250Fm ( Z =100, N = 150 )
Odd-Proton
251Md (Z = 101, N = 150)
255Lr
(Z = 103, N = 152)
Odd-Neutron
253No (Z = 102, N = 151)
Future plans
Spectroscopy of very neutron deficient
and heavy nuclei at JYFL
 Can be produced via fusion evaporation with stable-ion beams and stable targets
 Short-living alpha or proton emitters → tagging methods
 Cross-sections down to 1 nb
 Only levels near the yrast line populated
Recoil – Decay –Tagging (RDT)
method
RDT Instrumentation at JYFL
GREAT
Focal plane
spectrometer
TDR
Total Data Readout
Triggerless data acquisition system
with 10 ns time stamping
+ GRAIN the Analyser
SACRED electron spectrometer
at the RITU target
Transfermium Nuclei
Produced in asymmetric cold-fusion reaction – X(48Ca,2n)Y
→ ideal for the gas-filled separator RITU
→ Only one reaction channel open
→ Total compound cross-section down to 50 mb
→ Ibeam up to 30pnA on a 0.5mg/cm2 target in in-beam runs
Fission dominates: 100000 : 1
→ Ibeam limited by the Ge rate
→ Very low focal-plane rate
→ Enables long t1/2 – α – tagging
254No
Z = 102, N = 152
In-beam γ- rays from
208Pb(48Ca,2n) 254No
- 2µb
JUROGAM + RITU
943
842
S. Eeckhaudt et al. EPJ A26, (2005), 227
254No
Elevel [keV]
In-beam γγ coincidences from
3000
2750
2500
2250
2000
1750
1500
1250
1000
750
500
250
0
?
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
I [hbar]
SACRED + RITU data
254No-recoil
gated in-beam conversion
electrons from 208Pb(48Ca,2n) 254No
Discrete lines
+
M1 continuum
M1
P.A. Butler at al. PRL 89 (2002) 202501
254No
Levelscheme
R.-D. Herzberg et al. Nature 442, 896-899 (24 August 2006)
Short isomer
(16+)
Long isomer
83+
55 s
250Fm
Z = 100, N = 150
Singles Gamma-Ray Spectra from 204Hg(48Ca,2n)250Fm
(HgS targets)
A. Pritchard, R.-D. Herzberg et al., University of Liverpool
250Fm
electron spectra
250Fm
Tagged with
isomer
PT Greenlees, RDH et al, preliminary!
JUROGAM
preliminary
Levelscheme
250Fm
?
PT Greenlees, RDH et al, preliminary!
?
Kinematic moment of inertia J(1)
even – even nuclei
Dynamic moment of inertia J(2)
even – even nuclei
140
130
254
No
252
No
250
Fm
(2)
2
I [h /MeV]
120
110
100
90
80
70
60
0,05
0,10
0,15
0,20
Rotational frequency [MeV]
0,25
Dynamic moment
of inertia
even – even nuclei
250Fm
Dynamic Moment of Inertia J(2)
Theory:
M. Bender et al.,
NPA 723 (2003) 354
♦ Exp
250Fm
Kinematic and Dynamic Moment of
Inertia J(1) and J(2)
A Afanasiev, priv comm.
Kinematic and Dynamic Moments of Inertia
J(1) and J(2)
A. Afanasiev, PRC 67, 24309, (2002)
Odd - proton
251Md
150
,
255Lr
152
[514]7/2[521]1/2-
[633]7/2+
Electromagnetic Properties
• Odd-proton orbitals in 251Md / 255Lr
• B(M1)/B(E2) depends on (gK-gR)/Q0
[514]
72
gK ~ 0.7
Mainly E2
72
[633]
7+
2
gK ~ 1.3
Mainly M1
7+
2
[521]
12
a ~ 0.9:
Mainly E2
gK ~ -0.55
12
Conversion coefficients
Z ≈102
Prompt γ-ray spectroscopy of
251Md and 255Lr
205Tl(48Ca,2n)251Md
 ~ 760 nb
(A. Chatillon, Ch. Theisen et al. )
209Bi(48Ca,2n)255Lr
~ 300 nb
(S. Ketelhut, P. Greenlees et al.)
No signature partner : K=1/2
γγ coincidences
Recoil Tagging
First rotational band in an odd-Z transfermium
J (2) (hbar2MeV-1)
Dynamical Moments of Inertia J(2)
Rotational Frequency
251Md
Dynamic Moment of Inertia J(2)
Theory:
M. Bender et al.,
NPA 723 (2003) 354
7+
2
430
72
300
72
7+
2
200
185
7+
2
½-
½W.S.
S. Ćwiok et al.
HFB + SLy4
100
72
½HFB + Gogny
M. Bender et al. H. Goutte, priv. comm.
255Lr
209Bi(48Ca,2n)255Lr
– Recoil Tagging
255Lr
– Recoil Decay Tagging
Comparison 255Lr – 251Md
Odd - neutron
253No
151
The ground state of 253No is a neutron 9/2- [734] state
GREAT spectra from 207Pb(48Ca,2n)253No
1.7 min
100
Counts/5 keV
Counts/keV
125
γ rays
75
50
25
0
10
8
electrons
6
4
2
0
100
200
300
400
Energy [keV]
Confirmed by
F.P. Heßberger et al.
E.P.J. A 22, 417 (2004)
Earlier
Gammasphere+FMA
experiment
207Pb(48Ca,2n)253No
– 0.5µb
P. Reiter et al. PRL 95, 032501 (2005)
JUROGAM + RITU
Recoil-gated γ rays
from 207Pb(48Ca,2n)253No
Exp
It is not 7/2+[624] band
but 9/2-[734]
K=7/2 simulation
K=9/2 simulation
253No
It is not 7/2+[624] band
but 9/2-[734]
253No
SACRED + RITU data
In-beam conversion electrons from
207Pb(48Ca,2n) 253No
Exp
K=9/2 simulation
K=7/2 simulation
9/2- [734]
Indeed
P. Butler et al.
Dynamic moment of inertia J(2)
Theory:
M. Bender et al.,
NPA 723 (2003) 354
PERSPECTIVES
Improved sensitivity for in-beam studies:
• Digital signal processing → Higher counting
rate
Development of high-intensity beams
In-beam gamma - electron concidences for SHE:
• Combined gamma-ray and electron spectrometer SAGE
PERSPECTIVES
Improved sensitivity for in-beam studies:
• Digital signal processing → Higher counting rate
Development of high-intensity beams
• 50Ti + 208Pb → 256Rf + 2n
In-beam gamma - electron concidences for SHE:
• Combined gamma-ray and electron spectrometer SAGE
In-beam γ rays from 208Pb(50Ti,2n)256Rf – 12nb
700 recoils ↔ 25pnA, 1 week
Simulation – a random bit of the 254No experiment
256Rf
Z = 104
PERSPECTIVES
Improved sensitivity for in-beam studies:
• Digital signal processing → Higher counting rate
Development of high-intensity beams
In-beam gamma - electron concidences for SHE:
• Combined gamma-ray and electron
spectrometer - SAGE
SAGE
UK investment
SAGE
Collaborating institutes
Thank you for your attention !
Moment of inertia