W. Nörtershäuser 1

Addendum to IS 449

Measurement of the isotope

shift of 7,9,10,11Be at COLLAPS

Laser Spectroscopy of Highly Charged Ions and Exotic Radioactive Nuclei

(Helmholtz Young Investigators Group)

http://www.kernchemie.uni-mainz.de/laser/

The BeTINa Collaboration

W. Nörtershäuser1,2, K. Blaum1,2, J. Ebele4, Ch. Geppert2, M. Kowalska3, J. Krämer1, R. Neugart1, R. Sanchez1, F.

Schmidt-Kaler4, D. Tiedemann1, D. Yordanov3, M. Zakova1, C. Zimmermann5

1 Johannes Gutenberg-Universität Mainz, Germany 2 GSI Darmstadt, Germany3 CERN, CH-1211 Genéve 23, Switzerland4 Universität Ulm, Germany5 Eberhard-Karls Universität Tübingen, Germany

Spokespersons: W. Nörtershäuser, C. GeppertLocal Contacts: D. Yordanov, M. Kowalska

W. Nörtershäuser 2

Radii of Halo Isotopes

2004: 11Li at TRIUMF, R. Sanchez et al., PRL 96, 033002 (2006)

2003 : 6,7,8,9Li at GSI G.Ewald et al., PRL 93, 113002 (2004)

2004: 6He at Argonne, L.-B. Wang et al. PRL 93, 142501 (2004)

Charge radius measurements of light (Z<18) radioactive isotopes:

2007: 8He at GANIL, P. Müller et al. PRL 99, 252501 (2007)

W. Nörtershäuser 3

Isotope Shift

IS = MS +Field Shift|(0)|2 r2Z

3

FS

Mass Effect, nuclear motion

21 1

AAA

AA A

'

'MS

3

2

A

ZFS

= Frequency difference in an electronic transition between two isotopes

0.001 GHz10 GHzHe, Li, Be :

Isotop 1

Isotop 2

finite size of the nucleus

W. Nörtershäuser 4

Charge Radii Determination for Light Elements

IS = FS

2δ r

MS +

|(0)|22Z3

THEORYEXPERIMENT

|(0)|22Z3

Charge Radius :',AA

r 2δ',AAνmeasured ',AAν Theory MS,-

=C

I sotope 7 A,MS [Puch06] 7 A,

MS [Drake06] 6Li - 11 452.822 (2) (0) -11 452.83 (2) 8Li 8 634.990 (1) (1) 8 634.98 (2) 9Li 15 331.797 (3)(13) 15332.03 (3) 11Li 25 101.473 (9)(21) 25101.42 (3)

W. Nörtershäuser 5

Level Scheme and Be+ Transitions

0

5

10

15

Ene

rgie

[eV

]

0

20000

40000

60000

80000

100000

120000

140000

Ene

rgie

[cm

-1]

1s2 2s 2S1/2

1s2 2p 2P1/2, 3/2

3s

4s

5s

3p

4p

3d

4d 4f

7,9Be+

2s1/2F=1

F=2

2p1/2F=1

F=2

2p3/2 F=0,1,2,3

313.197 nm

= 8,1 (4) ns, ~ 20 MHz

313.197 nm

= 8,1 (4) ns, ~ 20 MHz

11Be+

2s1/2F=0

F=1

2p1/2F=0

F=1

10Be+

2s1/2

2p1/2

F=1/2

F=1/2

RF

W. Nörtershäuser 6

Simulated Spectra

-1000 -500 0 500 1000

F=

2 -

F=

1

F=

2 -

F=

2

F=

1 -

F=

1

F=

1 -

F=

2

F=

1 -

F=

0 F

=1

- F

=1

9Be

11Be

Am

plitu

de (

arb.

uni

ts)

Frequency (MHz, relative cg)

F=

0 -

F=

1

nat 20 MHz

2s½F=0

2p½F=0

F=1

11Be+

RF

F=1

W. Nörtershäuser 7

Why COLLAPS ?

• Standard collinear measurements are limited by the uncertainty of the acceleration voltageUse “simultaneous” collinear-anticollinear measurement and absolute frequency determination with a frequency comb

• Field shift is too small in light isotopesFS constant in Be+ 2s-2p is considerably larger than in lithium 2s-2p or 2s-3s since the electron is stronger bound

Charge radii can be measured to a good accuracy with COLLAPS if we apply "new" techniques !

W. Nörtershäuser 8

Approach

LASER 1

LASER 2

Ion beam

optic

alde

tect

ion

char

geex

chan

gece

ll

dece

lerat

ion

defle

ction

LASER 1

LASER 2

Ion beam

optic

alde

tect

ion

char

geex

chan

gece

ll

dece

lerat

ion

defle

ction

10p 10a

20

20

22 1 pa

Frequency Comb

W. Nörtershäuser 9

RF Comparator

Feedback

Dye Laser 2/2

Frequency Doubler 1

Laser

Beam 1

Collinear Laser Beam

Frequency Doubler 2

Laser

Beam 2

Anti-CollinearLaser Beam

/2 PBC

Dye Laser 1Nd:Yag Laser

Wavemeter

Frequency Comb

Iodine Spectroscopy

Feedback

Laser System for Beryllium Spectroscopy

W. Nörtershäuser 10

Iodine Lines for the 9Be+ 2s1/2 2p1/2 transition (cg)

46200 46400 46600 46800 47000 47200 47400 47600 478000.0

0.5

1.0

1.5

2.0

2.5

In

ten

sity

[arb

. un

its.]

Voltage [V]

W. Nörtershäuser 11

Measurement Procedure

I2

Voltage

Frequency

Frequency

Comb-Laser

W. Nörtershäuser 12

Be Hyperfine Measurements at COLLAPS

+ Mass shift calculations by G.W.F. Drake and Z.-C. Yan / K. Pachucki:→ Exakt position of Be Resonances within a few MHz

0 1450 2900 4350

Doppler-tuning frequency (MHz)

85 MHz

Previous successful beryllium measurement at COLLAPS

W. Nörtershäuser 13

Reachable Accuracy

Absolute frequency determinationLine center accuracy 1 MHz1 mrad Laser – Ion Beam Angle 0.005 MHz1 mrad Missalignment of laser beams 0.75 MHzClock-related comb uncertainty < 0.10 MHz

Total Uncertainty < 2 MHz

IS determination (differential effects)Line center accuracy <1 MHz1 mrad Laser – Ion Beam Angle 0.005 MHz1 mrad Missalignment of laser beams 0.075 MHz

Total Uncertainty ~ 1 MHz

W. Nörtershäuser 14

Beamtime Request and Schedule

• Test Beamtime in April / May ( 8 shifts)• On-line Run in June / July (16 shifts)

Summary : A nuclear charge radius determination of 7,9,10Be and the 1-Neutron Halo Nucleus 11Be with an accuracy of better than 5% Rc is feasible by frequency-comb based collinear laser spectroscopy at COLLAPS.

W. Nörtershäuser 15

Be-Isotope properties