nuclear structure research at isoltrap
DESCRIPTION
Nuclear structure research at ISOLTRAP. 17th of November 2008. Dennis Neidherr University of Mainz. Outline:. Motivation for our measurements Xe/Rn results Interpretation of the results Discovery of 229 Rn. determination of cyclotron frequency ( R = 10 7 ). B. 2 m. B = 5.9 T. - PowerPoint PPT PresentationTRANSCRIPT
Nuclear structure research at ISOLTRAP
17th of November 2008
Dennis Neidherr University of Mainz
Outline: Motivation for our measurements Xe/Rn results Interpretation of the results Discovery of 229Rn
www.quantum.physik.uni-mainz.de/mats
ISOLTRAP setupISOLTRAP setup
B = 4.7 T
B = 5.9 T
2 m
G. Bollen, et al., NIM A 368, 675 (1996)F. Herfurth, et al., NIM A 469, 264 (2001)
determination of cyclotron frequency(R = 107)
removal of contaminant ions
(R = 105)
Bunching of thecontinuous beam
B
+q/m
z0
r0
Bm
qc
2
1
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MotivationMotivation
Empirical correlation between Vpn values and growth rates of collectivity:
In the vicinity of closed shells the p-n interaction is expected to be large if protons and neutrons are filling similar orbits.
2,2,22,,4
1),( NZNZNZNZ
eepn BBBBNZV
1,2,21,,2
1),( NZNZNZNZ
eopn BBBBNZV
Interaction between the last proton(s) and neutron(s):
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Motivation Rn measurementsMotivation Rn measurements
Vpn values around A ~ 220:
113 117 121 125 129 133 137 141
100
200
300
400
500 Ra
Hg
PbV
pn(e
ven-
odd)
(ke
V)
Neutron number
Whereas the very large value for 208Pb is well understood, the sharp peak for Ra is still under investigation
Rn
Th
U
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N-rich Xe dataN-rich Xe data
Masses of 136-146Xe:
• For 143-146Xe only extrapolations were known so far
• 147Xe would have also been possible, but we had no time to try it; 148Xe was never observed at any experiment
• We obtained also some resonances of 138Xe, without influence of the expected contamination 138Ba
• The uncertainty of our measurements is in the order of 2-20 keV
136 138 140 142 144 146
0
100
200
300
400
500
600
700
800
900
1000
136 137-10
-5
0
5
10
ISO
LT
RA
P -
AM
E2
00
3 s
yste
ma
tics
(ke
V)
mass number
ISOLTRAP AME 2003
Neidherr et al, in preparation
www.quantum.physik.uni-mainz.de/mats
N-rich Xe dataN-rich Xe data
2-neutron seperation energies of 136-146Xe:
80 85 90 95 100 105 1106000
8000
10000
12000
14000
16000
18000
20000
QE
QF
QGQH
QIQJ QK
QL QM QNQO
QPQQ QR
QSQT
QUQV
QWQX
QYQZ
RA
rc
rdre rf
rg rhri rj rk
rl rmrn
rorp
rqrr
rs
rtru
rvrw
rx
S2n
(ke
V)
N
Sn Sb Te I Cs Ba La Ce Pr Nd Pm Sm Eu Gd Tb Dy
A Hoa Er
Tm Yb Xenew ISOLTRAP data
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220 222 224 226 228 230
-200
0
200
400
220-20
-10
0
10
20
IS
OL
TR
AP
- A
ME
20
03
sys
tem
atic
s (k
eV
)
mass number
ISOLTRAP AME 2003
N-rich Rn dataN-rich Rn data
6 masses were measured directly for the first time.
All these mass values were only extrapolated up to now.
Our uncertainties are always below 20 keV.
220Rn was used as a cross-check.
Masses of 223-229Rn:
124 126 128 130 132 134 136 138 140 142 1448000
10000
12000
14000
16000
18000
S2n
(ke
V)
Neutron Number
Pb Bi Po At Rn Fr Ra Ac Th Pa
new ISOLTRAP dataPb
Rn
Pa
Neidherr et al, submitted to PRL
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Interpretation of Interpretation of VVpnpn(Ra) data(Ra) data
For the Ra isotopes with an odd number of neutrons a very sharp peak at N=135 is visible.
This could be a hint for octopole deformation or a sub-shell clusure around N=134.
Here, the Vpn values for neighboring elements have similar behavior, but they are systematically shifted to the right for each successive Z.
A similar behavior is only known in the rear-earth region where it appears near mid-shell.
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229229RnRn
The question is, if this resonance is really 229Rn (which was never seen before at any measurement):
We have several proofs that it is indeed 229Rn:
i. The resonance was quite clean, so no contaminations were visible (which would lead to a decrease in the TOF effect)
ii. All possible molecular contaminations with up to three different species in the range of +/- 2 Hz can be excluded.
396579 396580 396581 396582 396583
440
480
520
560
600
Me
an
time
of
flig
ht /
s
C / Hz
229Rn+
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229229Rn (2)Rn (2)
iii. The yield is exactly behaving like expected. We saw roughly one order of magnitude less 229Rn than 228Rn.
219 220 221 222 223 224 225 226 227 228 229 230
100
101
102
103
101
102
103
104
Yie
ld a
t IS
OLD
E t
ape
stat
ion
(Ion
s / C
)
Yie
ld a
t IS
OLT
RA
P (
Ions
/
C)
Rn isotope
The black circles show the yield in our trap, whereas the red rectangles show the yield at the ISOLDE tape station
New arc-discharge ion source increased the ionization efficiency for nobel gases by a factor of 5 to 20.
Talk by L. Penescu, Wednesday 11:50 am
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229229Rn (3)Rn (3)
iv. Also the half-life of 229Rn was measured at the ISOLDE tape station. And it fits very well with the theoretical predictions.
0 200 400 600 800 1000 12000
2
4
6
8
10
12
14T
rf = 1.2 s
229Rn+Afterdecay
nu
mb
er
of i
on
stime of flight / s
Ratio ~ 18 %
0 200 400 600 800 1000 12000
5
10
15
20
25
30
nu
mb
er
of i
on
s
time of flight / s
228Rn+Afterdecay
Ratio ~ 8 %Trf = 1.2 s
T1/2 (228Rn) = 65 s T1/2 (229Rn) < 65 s
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229229Rn (3)Rn (3)
iv. Also the half-life of 229Rn was measured at the ISOLDE tape station. And it fits very well with the theoretical predictions.
222 224 226 228
101
102
103
104
105
0 50 100 150 200
0
50
100
150
200
250
300
rado
n is
otop
e ha
lf-lif
e (s
)
mass number
Time (s)
Co
un
ts
Result from the fit: 12 s (+1.2 s, -1.3 s)
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Outlook:Outlook:
Next steps:•158,160Sm:
A RILIS ionization scheme will be maybe tested this winter
• 154,156Nd:an ionization scheme has alreadybeen tested
Talk by V. Fedosseev, Tuesday 09:00 am
N
AME2003 data DFT calculations
• 116,118,120Pd:Determination of Cd-Vpn values,too low yield, so also further target development necessary
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Thanks to:Thanks to:
VH-NG-037
• ISOLTRAP collaboration: G. Audi, D. Beck, K. Blaum, Ch. Böhm, M. Breitenfeldt,
S. George, F. Herfurth, A. Herlert, A. Kellerbauer, M. Kowalska, D. Lunney, S. Naimi, M. Rosenbusch, S. Schwarz, L. Schweikhard
• And to:
R.B. Cakirli, R. Casten, E. Minaya-Ramirez, E. Noah,L. Penescu, T. Stora
• Funding:
Thanks a lot for your attention!