prospects for laser spectroscopy of superheavy...

Prospects for Laser Spectroscopy of Superheavy Elements

Hartmut Backe1, Michael Block, Mustapha Laatiaoui, Werner Lauth

1University of Mainz, Germany

International Symposium Super Heavy Nuclei 2015, Texas A&M University, College Station, Texas, USA, March 31 - April 02, 2015

Outline

1. Introduction and Motivation2. How Sensitive is Optical Spectroscopy? 3. Remarks on Laser Induced Fluorescence (LIF) Spectroscopy in a

Buffer Gas Trap4. RAdioactive Decay Detected Resonance Ionization Spectroscopy

(RADRIS)Optical Spectroscopy at Americium Fission Isomers (Z = 96)

5. Ion-Guide-Detected Resonance Ionization Spectroscopy (IGRIS)Investigation of the Atomic Level Scheme of Fermium (Z = 100)

6. RADRIS with the Ion Collection and Atom Re-Evaporation MethodStatus of Laser Spectroscopy at Nobelium (Z = 102)

7. Conclusion no le

vels

kno

wn

Met

hods

1. Introduction and Motivation

Pb83Bi

84Po

87Fr

88Ra

89Ac

35Br

53I

36Kr

54Xe

85At

86Rn

104Rf

105Du

106Sg

107Bh

108Hs

109Mt

11Na

12Mg

3Li

4Be

1H

13Al

5B

7N

14Si

6C

15P

16S

80

9F

17Cl

16Ar

10Ne

2He

58Ce

59Pr

60Nd

61Pm

62Sm

63Eu

64Gd

65Tb

66Dy

67Ho

69Tm

70Yb

71Lu

90Th

91Pa

92U

93Np

95Am

96Cm

97Bk

98Cf

99Es

101Md

102No

103Lr

110 111 112

Pu94

19K

20Ca

21Sc

22Ti

23V

24Cr

25Mn

26Fe

27Co

28Ni

29Cu

30Zn

31Ga

32Ge

33As

34Se

37Rb

38Sr

39Y

40Zr

41Nb

42Mo

43Tc

44Ru

45Rh

46Pd

47Ag

48Cd

49In

50Sn

51Sb

52Te

55Cs

56Ba

57La

72Hf

73Ta

74W

75Re

76Os

77Ir

78Pt

79Au

80Hg

81Tl

82

68Er

100Fm

6d25f 6d2 5f 6d3 5f7 5f 6d145f 6d4 5f 6d75f6 5f9 5f10 5f11 5f13 5f145f12

Ds114

Uuu Uub Uuq

Why Atomic Spectroscopy of Heavy Elements?

58Ce

59Pr

60Nd

61Pm

62Sm

63Eu

64Gd

65Tb

66Dy

67Ho

68Er

69Tm

70Yb

71Lu

90Th

91Pa

92U

93Np

94Pu

95Am

96Cm

97Bk

98Cf

99Es

100Fm

101Md

102No

103Lr

Actinides

Lanthanides

no atomic spectroscopic data available

Periodic Table

Relativistic Effects for Atomic Level Scheme of Uranium

Stabilization ofs1/2, p1/2 Orbitals

Destabilization of d, f Orbitals

finite c

Spin-OrbitCoupling

non-relativistic relativistic

-60

-50

-40

-30

-20

-10

0

6s1/2

6p1/2

6p3/2

5f5/2

5f7/2

6s

6p

5f

6d7s

{E

[eV

]6d3/2, 6d5/27p1/2, 7p3/27s1/2,

c

rela-tivistic

Z*

r /a0

P(r

)

Radial Wave Functions of Relevant Orbits in PuNon-relativistic Hartree-Fock calculations taken from E. F. Worden , Jean Blaise, and Mark Fred and N. Trautmann and J.-F. Wyart The Chemistry of the Actinide and Transactinide Elements, Third Edition (2008)

(0)I Nuclear magnetic moment

eI HAIJ

Hyperfine structure interaction1. Magnetic dipole hfs

2. Electric quadrupole hfs

(0) jjS SB Q Qe Spectroscopic quadrupole moment

3. Coupling

Nuclear spin IJ F I

Isotope shift

<r2> A,A’ change of mean square charge radius

Nuclear Ground-State Properties by Atomic Physics Techniques

Requirements for Optical Spectroscopy at Trans-Einsteinium Elements

6 m 28 m

21.5 s 25.9 s 0.6 s

1.3 h3.1 m55 s

Off-line: Z 100 (Fm) breeding of material in high flux isotope reactors

Problem: Experiments at Fm with typically 1010 atoms only

On-line: Z > 100 Nuclear reactionstargets : Pb,U,Pu,Cm,Cf, Es beams : p,d,,HI (Ca)

209Bi

208Pb

No

atom

ic

spec

tros

copi

c da

ta a

re k

now

n

Problem: at σ ~ µb small production rates ~1/s 254Md253Md 255Md

252Fm25.4 h

254No 255No 256No

255Lr 256Lr 257Lr

253Fm 254Fm 255Fm

253Es

3 d 3.24 h 20.1h

252Es251Es

Ultra-sensitive Laser-Spectroscopic Methods

2. How Sensitive is Optical Spectroscopy?

How Sensitive is Optical Spectroscopy?

R.G.Voe et al., PRL 76 (1996) 2049(Toschek, Dehmelt, Neuhauser et al., 1980)

First example: Ba+ stored in an ion trap

2102

0 cm 102

)( i

kr g

g

Transition rate per atom )(1)( 00

rrik dAdP

dANdP

Power of tuneable cw dye lasers P 100 mW ... 1 W

“In principle” only 1 atom required

Flux of photons 17 18 810 ...10 / ( ) 10 / ( )2s cm s atom

ikdN PdA

Buffer Gas Trap

Radioactive Ionsfrom SeparatorT1/2 >1 ms

Buffer Gas Cell

He, Ar at 100 mbar

RIDiffusion

50 ms

1-2 cm

+

++

+ + +

+

+

+

+

+

+ ++

+

+++

+ 85% charged

15% neutral

• Laser Spectroscopy at Neutral Fraction• Ion Chemistry and Drift Time Measurements at Charged Fraction• Cooling and Bunching and Transfer to Traps for Mass Measurements

3. Remarks on Laser Induced Fluorescence (LIF) Spectroscopy

in a Buffer Gas Trap

Laser Beam

HI beam

Target

Recoil Distribution

PM

TAC

time

time

Signal

Background

LIF Signal

Laser Induced Fluorescence (LIF) Spectroscopy

G. D. Sprouse et al., Laser Spectroscopy of Light Yb Isotopes On-Line in a Cooled Gas Cell. Phys. Rev. Lett. 63 (1989) 1463Sensitivity: Target production rate about 103/s

4. RAdioactive Decay Detected Resonance Ionisation Spectroscopy

(RADRIS)Optical Spectroscopy at Americium

Fission Isomers (Z = 96)

RAdioactive Decay Detected Resonance Ionisation Spectroscopy (RADRIS)

0.9ms 1.0ms

Americium Fission Isomers

Aim: <r2>, Q20, I, gwith Optical Spectroscopy

240fAm (T1/2= 0.9 ms)242fAm (T1/2=14 ms)244fAm (T1/2=1 ms)

Dubna 1962

•conversion electron spectroscopy•lifetime measurements of excited states (charge plunger

method)•g-factor measurements• -ray spectroscopy•optical spectroscopy

d Beam 6ms on / 6ms off 12 MeV, I=3A p Beam 2ms on / 2ms off 24 MeV, I=3Ad Beam 2ms on / 2ms off 14 MeV, I=2A

242Pu (d,2n) 242fAm T1/2=14ms242Pu (p,3n) 240fAm T1/2=0.9ms244Pu (d,2n) 244fAm T1/2=1ms

0 10 20 cm

Accelerator(95 kV)

Einzel - Lens System

q~20+

5/sPu Target

60 kV 50 kV

f - Isomer Beam

=(8±3)b

f Detector

Buffer Gas Cell40 mbar Ar

Anti-CoincidenceDetector

Monitor Detector

Getter (350 °C)

Laser

H. Backe et al., PRL 80 (1998) 920

Experimental Setup

19994 20003 200040,0

0,5

1,0

1,5

RIS

-f C

ount

s [1

/mC

]C

harg

e [a

.u.]

240fAm (x2)

242fAm

0.559(32) cm-10.250(5)cm-1

241Am 243Am

10.358(14)cm-10,0

0,5

1,0

At variance with

X240f = 26.8 (2.0) (Bemis et al.)

242Pu(d,2n)242fAm, =8 b, 12 MeV242Pu(p,3n)240fAm, =8 b, 24 MeV

500.02nm50 J/cm2

351,353nm2 mJ/cm2

48179

0

19993/ cm

-1

Laser = 1.5 GHz

242f,2

24242f

exp ,2 1

1

3 4

4

I( Am) 41.4 (8)

SIS

X

240f,2

24240f

exp ,2 1

1

3 4

4

I( Am) 39.2 (8)

SIS

X

Isotope Shift Measurement in the Second Potential Minimum

-1[cm ]

_

232 236 2405

101520253035404550 U

A

Q20

[eb]

236 240 244

Pu

240 244

Am

244 248 252

Cm

Quadrupole Moments of Fission Isomers

Charge Plunger

Axes ratio 1:1.9

5.Ion-Guide-Detected Resonance Ionization Spectroscopy (IGRIS)

Investigation of the Atomic Level Scheme

of Fermium (Z = 100)

t1/2 = 4730 a

High Flux Isotope ReactorOak Ridge National Laboratory

246Cm

249Bk

249Cf

253Es255Es

•Chemical Separation of Es,

• Waiting for 255Es 255Fm decay

• Chemical Extraction of 255Fm ( t1/2= 20.1 h )

Air Shipmentto Germany

Bake OutEvaporationTests

Electrochemical Production ofFilaments at Mainz

0.9 ng 255Fm at Oak Ridge, USA

1 2 3 4 51x1010

1x1011

1x1012

FrThWeTuMoTime [d]

LaserSpectroscopy

• Breeding of 255Es (Z = 99)n = 2.6 . 1015/cm2 . s

t = 1 a

Production of 255Fm

1/2

-

39.8 dt

tantalum filament

titanium layerelectrolyticallydepositedFm-hydroxide

QMS

ChanneltronDetector

Ion OpticsSegmentedPaul Trap

90°

Deflector

0 5cmTMP

700 l/sTMP

230 l/sTMP

360 l/sTMP

330 l/s


Nozzle

Electrodes


LaserBeams

Filament

Ion-Guide Detected Resonance Ionization Spectroscopy with Mass Selective Ion Detection

Detuning Laser 1

Cou

nts

h1h

h

h

h

Determinationof the IPIP

26000 28000104

105

106

107

108

109

5f127s7p

MCDF CalculationsS. Fritzsche, C.Z.Dong (5f127s7p)

5I65H5

3I53G5

3H6

A ki

[1/s

]

[cm-1]

ground state5f127s2 3He

6

12400 cm

Theoretical Level Predictions for Fermium

Optical Parametric Oscillator (OPO) :~4 cm-1 (120 GHz )

SHG THG

BBO-OPO SHG

Nd-YAG Laser50 Hz, 550 mJ

532 nm~200 mJ

355 nm50 mJ

410 ---- 1000nm~ 10 mJ

205 ---- 400 nm~1mJ

Excimer Laser500 Hz, 60 mJ/PulsLambda Physics

EMG104 MSC Dye

351 nm353 nm

Bandwidth: 0.05 cm-1 (1.5 GHz)

Excimer Laser100 Hz, 200 mJ/Puls

Lambda PhysicsLPX

308 nm

Dye Lasers, Bandwidth: 0.2 cm-1 (6 GHz)MainTrigger

Dye Dye Dye Dye

308 nm50 mJ

351 nm20 mJ

> 390 nm~ 3 mJ

> 350 nm~ 5 mJ

Laser SystemsXeF

XeCl

M. Sewtz et al., Phys. Rev. Letters 90 (2003) 163002

Excimer351/353 nm

The First Optical Transition ever Observed for Fermium (Z = 100)

IP

25100

52400

0

2

_

1

_

[cm-1]_

351/353 nm

10.3 cm

2

mJ2cm

(352 – 380) nm

27385 27390 273950

5

10

15

20

27465 274700

10

20

30

40

50

28185 281900

50

100

150

200

28375 283800

1020304050607080

28385 28390 283950

20

40

60

80

100

120

25000 26000 27000 280000

50

100

150

200

R6 R7R5R4R3

Cou

nts

[cm-1] [cm-1] [cm-1] [cm-1]

Cou

nts

[cm-1]

Cou

nts

Cou

nts

Cou

nts

Scan RegionScan Region

C

ount

s

[cm-1]

Summary of Level Search

Aki ≥ 1.5 ּ◌107Aki ≥ 5.2 ּ◌106

6. RADRIS with theIon Collection and Atom Re-

Evaporation Method Status of Laser Spectroscopy

at Nobelium (Z = 102)

Experimental Setup208Pb (48Ca,2n) 254No (t1/2=55 s, a decay)

3.4 b: 5 Ions/s

The Ion Collection and Atom Re-Evaporation Method (ICARE)

Heavy ion beam(highly charged,40-90 MeV)

Buffer Gas CellAr at 50-100 mbar

Method take advantage of the85 % charged fraction

15 % neutrals

85 % charged

Radioactive Decay Detected Resonance Ionization with the ICARE Method

0 1 2 3 4 5 6

Collecting on DetectorCollecting on FilamentBeam offBeam on

Time [s]

Heat Pulse

Lasers

10 cm

-

Detector

Filament(Tantal)

+

++

RecoilBeam

LaserBeams

BufferGas

Pulsed

0

10000

20000

30000

40000

50000

60000

0.0

1.2

2.5

3.7

5.0

6.2

7.4

Exci

mer

lase

r 350

nm

MC

DF

calc

. S.F

ritzs

che

This

pro

ject

is s

aved

to

C:\U

sers

\Lau

th\D

ocum

ents

\Kon

fere

nzen

-Pap

ers\

2006

-Fra

uenw

oerth

\No-

leve

ls-L

aser

s

Nd

YAG

355

nm

OPO

-SH

G

Cou

pele

d C

lust

or, K

aldo

r

5f147s7p 1P1

5f147s7p 3P1

IP 50443 cm-1IP 53600 cm-1

870 ns

5,2 ns

14,6 ns

70 ns14 ns

4f146s6p 3P1

4f146s6p 1P1

E /

eV

4f135d6s2

4f135d6s2

4f146s7p

Theo

rie

Dye

lase

rs

[Rn]5f147s2 1S0

[Xe]4f146s2 1S0

Z=102Z=70

NoYb

/ cm

-1

TheoreticalPredictions

IP 53600 cm-1

Nobelium as Chemical Homolog of Ytterbium

4.0 4.5 5.0 5.50

200

400

600 Laser off

-Energie [MeV]

154Tm 154Yb155Yb152Er

156Yb

151Ho151Ho

150Dy

0

200

400

600 Laser on

Even

ts

154Yb

155Yb

152Er156Yb

151Ho151Ho150Dy

Test of the Method at 155Yb (Z=70)

λ2 = 399.6 nm

Laser 1

Laser 2

λ1 = 398.9 nm

SignalBackground

301=

107Ag(52Cr, p3n)155Yb (t1/2=1.75 s, - decay); = 15 mb, d = 0.455 mg/cm2, 4·104 Ions/s

Efficiency

Target

RI

Yb

S2Yb

NN 0.8 10

0.5 0.7 0.85 0.8 0.59 0.16 1 0.36

2SHIP Cell Ion Collect Decay Evap RIS Transp. Det0.8 10

Predictions for the 1P1 – level[1,2] (MCDF) S. Fritzsche, Eur. Phys. J. D 33, 15 (2005)

[3] (IHFSCC) A. Borschevsky et al., Phys. Rev. A 75, 042514 (2007)

[5] (MCDF) Y. Liu, R. Hutton, Y. Zou, Phys. Rev. A 76, 062503 (2007)

[6] (MCDF) P. Indelicato et al., Eur. Phys. J. D45, 155 (2007)

[4] (RCC) V.A. Dzuba et al., Phys. Rev. A 90 (2014) 012504

[7] (Extrapolation) J.Sugar, J. Chem. Phys. 60 (1974) 4103

Multi-Configuration Dirac Fock (MCDF)Intermediate Hamiltonian Fock-space coupled-cluster (IHFSCC)Relativistic coupled cluster (RCC)

Search for an Atomic Level

7. Conclusions• Resonance Ionization Spectroscopy (RIS) in gas cells is a

powerful laser spectroscopic method at samples in the order of only 1010 atoms or production rates as low as 1/s.

• 240-244fAm 0.9–14 ms on-line 106 - 107 RADRIS• 255Fm 20.1 h off-line few 1010 IGRIS

Prospects• 254No 55 s on-line 106 - 107 RADRIS• Method has been tested with an on-line laser spectroscopy

experiment at the chemical homologue 155Yb. An overall efficiency of ~ 1% has been measured.

• The experiment at 254No at GSI for an atomic level search is well prepared but is difficult and requires a lot of beam time.

• Activities are also underway at KU Leuven (Belgium) within the Heavy Element Laser Ionization Project (HELIOS) to be performed at the SPIRAL-2 facility at GANIL (France).

no a

tom

ic n

leve

ls k

now

n

H. BackeM. DahlingerA. DretzkeM. HiesT. KolbH. KunzP. KunzW. LauthP. SchwambM. Sewtz

K. EberhardtC. GrüningP. ThörleN. TrautmannJ.V. Kratz

Institut fürKernchemie

Universität MainzGermany

Institut fürKernphysik


Institut fürPhysik


ORNLOak Ridge

USA

Max-Planck-Institutfür Kernphysik

HeidelbergGermany

R.G. Haire

G. GwinnerR. RepnowD. Schwalm

G. HuberJ. LassenG. Passler

D. AckermannM. BlockF.-P. HeßbergerS. HofmannH.-J. KlugeM. Laatiaoui

GSI Helmholtzzentrum für

SchwerionenforschungGermany

Institut für Angewandte Physik

Technische UniversitätDarmstadt, Germany

F. LautenschlägerTh. WaltherHelmholtz-Institut

Mainz, Germany

M. BlockM. Laatiaoui

TRIUMFVancouver, Canada

P. Kunz

prospects for laser spectroscopy of superheavy...

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