Nuclear structure research at ISOLTRAP

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


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):


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


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


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


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


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.


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+


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


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


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)


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


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!

Nuclear structure research at ISOLTRAP

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