Laser spectroscopy on nuclear ground states for charge radii and moments.

Some new developments

Laser spectroscopy on nuclear ground states for charge radii and moments.

Some new developments

Thanks to: Jon Billowes, Paul Campbell, Iain Moore, H.-J. Kluge

For a review up to 2002, see: H.-J. Kluge and W. Nörtershauser , Lasers for Nuclear Physics,Spectrochim. Acta B 58 (2003) 1031

Laser Spectroscopy

Investigation of� Hyperfine structure� Isotope shifts� Isomer shifts

provides model-independentdata…

Optical techniques provide the sensitivity and precision requiredto measure these effects.

The nucleus is not a point charge –the atomic energy levels are perturbedby the electric and magnetic fieldsat the nucleus (part per million effects)

Isotope Shift (IS) Hyperfine Structure (HFS)

AAr

′2δ

Nuclear Spin IMagnetic Dipole Moment µI

Electric Quadrupole Moment Qs

Hyperfine Anomaly

Mean Square Charge Radii

Sample preparation is crucial…..Nuclear reaction products must be slowed and thermalizedquickly, efficiently, universally and selectively.

Thermal or discharge ion source+ isotope separator

Gas stoppers and beamcoolers

Introduction to laser spectroscopy

Ion source (40kV)Laser

PMT

Gat

es

Tun

ing

volta

ge

Isotope Shifts

� δ<r2> Size� δ<β2

2> Shape� δσ Diffuseness

Hyperfine Structure

� µ µ µ µ� Qs � <β2>

Present status of laser spectroscopy measurementsPresent status of laser spectroscopy measurements

Mass & decayspectroscopy

Collinear laser spectroscopy

Ion guide & laser ionsource trap

RFQ cooler & buncher – opticalmanipulation techniques

FURIOS laser cabin

The IGISOL Beamline at JYFLThe IGISOL Beamline at JYFL

COLLINEAR LASER SPECTROSCOPY WITH BUNCHINGCOLLINEAR LASER SPECTROSCOPY WITH BUNCHINGIGISOL: E ~ 40 keV, δδδδE ~100 eV

DC-cooler: δδδδE < 1 eVtransmission > 60%

Buncher: Accumulation time 10 ms - 10 s

Buffer gas cell, pHe ~ 0.1 mbar

DecelerationCollisional cooling in an

RF-quadrupole Acceleration

Beam in Beam out

40 kV

Turbo pump500 l/s

Turbo pump1300 l/s

Turbo pump900 l/s

High vacuum 10-6 mbar

Intermediate vacuum 10-4 mbar Electrodes

HV isolator

Laserbeam

174Hf

2·104 improvement of SNR !

+40 kV

Ion beam cooler

Light collection region

(Laser resonance fluorescence)

Trap and accumulates ions – typically 100 - 500 ms

Reduces energy spread of ion beam (100eV → 1eV)

Improves emittance of ion beam

Releases ions in a 10 µs bunch

Cooler advantagesCooler advantages

Cooling for laser spectroscopy

Reduced peak skewingz

V

End plate

Emittance: �3 π mm.mrad

Less spectral broadening

Better laser-ion overlap

He buffer gas

Energy spread: 100�1 eV

Bunching for laser spectroscopy

zEnd

pla

te p

oten

tial

Accumulate

Release

Cou

nts

100

2005.25 hours 8000 ions/s

100V

Before

Cou

nts

0

3048 minutes 2000 ions/s

After

PMT

20µs gate

Background eg. 200ms accumulation=20µs gate widthsuppression ~10

4

96-102Zr ~ 3000 ions/s 100Zr~ 500 ions/s 96Zr

Some recent highlights – but first an older measurementSome recent highlights – but first an older measurement

Deformed nucleus

Spherical nucleus

Zr charge radii measurement at IGISOL

P. Campbell et al., Phys. Rev. Lett. 89 (2002) 082501

Droplet modelMyers & Schmidt, Nucl. Phys. A410 (1983) 61.

Mass number

<r2 >

(fm

2 )

84 86 88 90 92 94 96 98 100 102 10418.4

18.8

19.2

19.6

20.0

20.4

20.8

80 100 12018

19

20

21

22

<β2>=0.0

<β2>=0.1

<β2>=0.2

<β2>=0.3

<β2>=0.4

40Zr

(Very similar to 38Sr behaviour)

Radii predictions for 40Zr from B(E2) valuesRadii predictions for 40Zr from B(E2) values

Big discrepancies between B(E2)measurements and charge radii. Butfor A=96 to 100, nuclear spins areeither 0 or ½: NO measureablequadrupole moments…..….look at yttrium (+isomers).

• Shape change at N=59

• 98m is well deformed

39Y isotopes and isomers 39Y isotopes and isomers

I=0 I≠0 Prolate

ββββ 2222 =0.0=0.0=0.0=0.0

ββββ 2222 =0.1=0.1=0.1=0.1

ββββ 2222 =0.2=0.2=0.2=0.2

ββββ 2222 =0.3=0.3=0.3=0.3

ββββ 2222 =0.4=0.4=0.4=0.4

ββββ 2222 =0.5=0.5=0.5=0.5

17,8

18,2

18,6

19,0

19,4

19,8

20,2

84 86 88 90 92 94 96 98 100 102 104Mass Number, A

<r2 >A

/ fm

2

Stable IsotopesRadioactivesIsomers

Yttrium charge radii Yttrium charge radii

Optical manipulation in the RF cooler-buncherOptical manipulation in the RF cooler-buncher

In some isotopes of yttriumthe nuclear spin is uncertain.We can manipulate the atomicstate to provide a better startingpoint for collinear work

This is done by “opticallypumping” the yttrium in theRF cooler – a new technique!

363.3nm pumping (40% transfer)

1pA of 89Y continuous beam

Indifference to bunching

Use broadband pulsed lasers with high repetitionrates (10 kHz)

Laser spectroscopy of niobium

322n

m

286n

m

Ground state2356.76cm-1

J=1

J=2

50% increase due to pumping � 1 photon per 2700 ions

Mass & decayspectroscopy

Collinear laser spectroscopy

Ion guide & laser ionsource (trap)

RFQ cooler & buncher – opticalmanipulation

FURIOS laser cabin

The IGISOL Beamline at JYFLThe IGISOL Beamline at JYFL

~6 eV(5-9 eV)

groundstate

firstexcitedstate

higher excitedstates

ionizationpotential

E1

ener

gy

0 eV E0

non-resonant ionization

excitation ofauto-ionizing states

field ionization ofRydberg-states

extractionfield

Principles of Resonance IonizationPrinciples of Resonance Ionization

Y. Kudryavtsev,- NIM B179 (2001) 412M. Facina,- NIM B224 (2004) 401M. Setwz,- PRL 90 (2003) 163002

0 2 4 6 8 10 12

270

300

330

360

390

Mea

n T

OF

/ µ

s

νc - 1300610 / Hz

��

�

16%

4%

80%

Intensity ratio:

normalized to the area

Unambiguous state assignment!ωc = � B

qm

R ≈≈≈≈ 1·107, δδδδm/m ≈≈≈≈ 4 ·10-8

ME of ground state is 240 keV higher than literature value!

270

300

330

360

390

Mea

n T

OF

/ µ

s

270

300

330

360

390

Mea

n T

OF

/ µ

s

�

�

�

with cleaning of 6– state

⇒⇒⇒⇒ (6–) state = gs

⇒⇒⇒⇒ (3–) state = 1 st is.

⇒⇒⇒⇒ 1+ state = 2 nd is.

101(3) keV101(3) keV

242(3) keV242(3) keV

J. Van Roosbroeck et al., Phys. Rev. Lett. 92, 112501 (2004).

Example on RILIS: Triple Isomerism in 70Cu (RILIS & ISOLTRAP)

Fast Universal Resonant laser IOn SourceFast Universal Resonant laser IOn Source

Ti:Sapphire lasers pumpedby Nd:YAG (12 kHz)

Pulsed dye lasers,pumped by CVL (12 kHz)or by 50 Hz Nd:YAG

I.D. Moore, J. Phys. G 31 (2005) S1499

CW dye lasers

Full spectral coverage at a range of repetition rates,linewidths and powers….

Laser development forapplications of in-sourcespectroscopy

A laser ion guide for heavy-ion fusion evaporation reactionsA laser ion guide for heavy-ion fusion evaporation reactions

A laser ion guide for heavy-ion fusion evaporation reactionsA laser ion guide for heavy-ion fusion evaporation reactions

Laser ion source trap technique at IGISOLLaser ion source trap technique at IGISOL

I.D. Moore et al., AIP Conference Proceedings Series, 831 (2006) 511.

Laser spectroscopyat the dripline

Isotopes with smallproduction rates atISOL facilities

Heavy neutron richisotopes

Next generation on-line facilities, SLOWRI at RIKEN and LASPEC at GSI.Much of the work can still be done at present facilities, eg at IGISOL, JYFL.Next generation on-line facilities, SLOWRI at RIKEN and LASPEC at GSI.Much of the work can still be done at present facilities, eg at IGISOL, JYFL.