Maxim Seliverstov

In–source Laser Photoionization Spectroscopy of 191-218Po isotopes at

ISOLDE

ISOLDE Workshop and Users meeting 200918-20 November 2009 CERN

In–source Laser Photoionization Spectroscopy of 191-218Po isotopes at ISOLDE

IS 456: Study of polonium isotopes ground state properties by simultaneous atomic- and nuclear-spectroscopy

Collaboration: CERN/ISOLDE - IKS Leuven-Mainz University- PNPI Gatchina- IPN Orsay

A.N. Andreyev, S. Antalic, A.E. Barzakh, B. Bastin, J. Billowes, J. Büscher, T.E. Cocolios, I. Darby,W. Dexters, D.V. Fedorov, V.N. Fedosseev, K. Flanagan, S. Franchoo, S. Fritzsche, G. Huber, M. Huyse, M. Keupers, U. Köster, Yu. Kudryavtsev, B.A. Marsh, P. Molkanov, M.D. Seliverstov, M. Sjödin, J. Van de Walle, P. Van Duppen, M. Venhart, S. Zemlyanoy, Yu. Volkov3

ISOLDE Workshop and Users meeting 200918-20 November 2009 CERN

In–source Laser Photoionization Spectroscopy of 191-218Po isotopes at ISOLDE

ContentsMotivationIn-source resonant photoionization spectroscopy at ISOLDEIsotope shifts and charge radii for even-A neutron-deficient Po isotopes:

A = 192-198 A = 200-210 A = 200-218

Hyperfine structure of the odd-A Po isotopes and isomers Conclusions and outlook

ISOLDE Workshop and Users meeting 200918-20 November 2009 CERN

Motivation

ISOLDE Workshop and Users meeting 200918-20 November 2009 CERN

nuclear ground and isomeric state properties : δ r 2

100 105 110 115 120 125 130

Pt (Z = 78)

Bi (Z = 83)

Po (Z = 84)

Hg (Z = 80)

N =

104

N =

126

r 2 ,

fm2

N

, Ground states , Isomers

Pb (Z = 82)= 0.1 fm2

Level systematics for the neutron-deficient polonium isotopes.R. Julin et al., J. Phys. G: Nucl. Part. Phys 27 R109 (2001).

????

????

6p4 3P2

6p37s 5S2

6p37p 5P2

Continuum

Po ground state

λ1 =255.8 nm

λ2 = 843.38 nm

λ3 = 510.6 nm (CVL) or 535 nm (Nd:YAG)

hfs0

hfs1

hfs2

8.4168 eV

In–source Laser Photoionization Spectroscopy at ISOLDE

Laser Ion Source (LIS)target

ionizer

Laser beams

Mass separator

Isotope shift, dr 2

I , Q S

Detection:Faraday Cupα-detection (Windmill)β-detection (tape-station)γ-detection (tape-station)

*

*This tranistion was already used for optical spectroscopy (Kowalewska et al, Phys. Rev. A, 44 R1442, 1991.)

Photoionization scheme for PoT.E. Cocolios et al. NIM B 266 (2008)

4403

Isotope shifts of the even-A Po isotopes

11853.2 11853.4 11853.6 11853.8 11854.00

50

100

Wavenumber, cm-1

192Po

0.0

0.5

1.0

194Po

0

50000

196Po

0

2000

4000

198Po

020004000

200Po

0

10000

20000

202Po

0

1000

2000204Po

0.0

0.2

0.4206Po

0.0

0.4

0.8208Po

0.00.20.40.6

210Po

0

400

800216Po

0500

10001500

218Po

ion

curre

nt

Isotope shift A,A’:

dA,A’= F * lA,A’ + (NMS+SMS)Rms charge radius :

lA,A’ = r 2 + C2dr 4 + … ≈ 0.93 dr 2

A ΔνA,196 , MHz T1/2, s Detection

192 –1037(150) 32 ms α

194 –372(120) 392 ms α

196 0 5.56 s α

198 –162 (130) 1.77 m α

200 –905(40) 11.5 m γ

202 –2009(100) 44.7 m β

204 –3315(50) 3.53 h γ

206 –4692(60) 8.8 d FC

208 –6104(60) 2.9 a FC

210 –7735(45) 138 d FC

216 –16555(55) 145 ms α

218 –19259(75) 3.1 m αPreliminaryT1/2 =33

ms<1 ion/s

Isotope shifts for 200-210Po:λ=255 nm and λ=843 nm

0 20000 40000 60000 800000

-10000

-20000

-30000

-40000

A,A'843

A,A'255

F843/F255= 0.45(3) from King plot

King plot:

F255 =29140 MHz/fm2

F843 = -12976 MHz/fm2

F843/F255= 0.44

Limited knowledge on the atomic structure of polonium: the electronic F-factor for the transition of interest in unknown.

Previous work by Kowalewska et al. is locked on the FRDM at A=206-208 to extract the F-factor for the transition at 255.8 nm.

Large-scale electronic computations by S. Fritzsche using the GRASP code also give the F-factor from a theoretical approach for both transitions.

ΔσA,A’ = ΔνA,A’ AA’/(A-A’)

Charge radii for 192-218Po

Preliminary105 110 115 120 125 130 135

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

d r2

, fm

2

N

Our data (new) Our data

N = 126

The experimental error bars are smaller than the symbol size.

Charge radii of neutron-deficient Po isotopes

95 100 105 110 115 120 125 130

Pt (Z = 78)

Po (Z = 84)

Hg (Z = 80)

N =

104

N =

126

r 2 ,

fm2

N

Ground state Isomer Spherical Droplet

model prediction

Pb (Z = 82)

= 0.1 fm2

The experimental error bar is smaller than the symbol size. The distance between the different chains is chosen arbitrarily for better display. One minor division on the vertical scale corresponds to 0.1 fm2Preliminary

Charge radii of neutron-deficient Po isotopes: shell-closure effect at N = 126

115 120 125 130 135 140 145 150

Rn (Z = 86)

Po (Z = 84)

Ra (Z = 88)N =

126

r 2 ,

fm2

N

Pb (Z = 82)

= 0.1 fm2

Preliminary

Elementdr 2N,N-2(N>126)––––––––––––––––dr 2N,N-2(N<126)

Pb 1.9

Po 2.1

Rn 2.2

Ra 2.2

Hyperfine structure of the odd-A Po isotopes

Odd-A Po isotopes: preliminary analysis

0

5000

10000

15000

E

0

10000

20000

High spin spin (13/2)

Low spin (3/2)

11853.6 11853.8 11854.0 11854.2

0

20

40

195Po

193Po

11853.6 11853.8 11854.0 11854.20

1020

30

4050

60

Wavenumber, cm-1Wavenumber, cm-1

0

500

1000

1500

2000

2500

197Po

0

10000

20000

Odd-A Po isotopes: preliminary analysis

100 102 104 106 108 110 112 114 116 118 120 122 124-1.6

-1.4

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

3p3/2

n

.m.)

N

, Pb, I = 13/2, Pb, I = 3/2

Hg, I = 13/2 Po, I = 3/2 Po, I = 13/2

1i13/2

Lit. data

Estimations (preliminary) of magnetic moments (193-197Po):

Preliminary!…to be continued191Po, 199-203Po…

Conclusions and outlook

Extension of the laser spectroscopy studies to the neutron deficient and neutron reach isotopes (and isomers) of Po: from 191Po to 218Po:

Isotope shifts for the even-A 192-218Po are extractedData on charge radii of 192-218Po are obtained, but the analysis is ongoing…Large and early departure of the charge radii from the Sperical Droplet Model prediction was observed for neutron deficient Po isotopesNeutron shell closure effect (around N = 126) was observed Spectra of the odd-A 191-211Po are obtained. Extraction of the isotope shifts and hyperfine splitting constants is ongoing…Some interesting effects are expected: dramatic change of the magnetic moments for the light Po isotopes, inverse odd-even staggering…

Thank you for your attention

Comparison with the theory

This picture has all the data and calculation that we have available at the moment. It is very crowded but it is also complete.

the BMF calculations are on private communication from P.-H. Heenen