Nuclear charge radius determination of the halo nucleus Be-11

Monika Žáková, Johannes Gutenberg-Universität Mainz

6 7 2 3 1 1 1 M. Bissell , K. Blaum , Ch. Geppert , M. Kowalska , J. Krämer , A. Krieger , R. Neugart , W. Nörtershäuser1,2 , R. Sanchez1, F. Schmidt-Kaler4, D. Tiedemann1, D. Yordanov7, C. Zimmermann5

1 Johannes Gutenberg-Universität Mainz, Germany Laser Spectroscopy of Highly Charged 2 GSI Darmstadt, Germany Ions and Exotic Radioactive Nuclei 3 CERN (Helmholtz Young Investigators Group) 4 Universität Ulm, Germany 5 Eberhard-Karls Universität Tübingen, Germany

6 Instituut voor Kern- en Stralingsfysica, Leuven

7Max Planck Institut für Kernphysik, Heidelberg

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

► Halo Nuclei

► Isotope Shift

► Collinear Laser Spectroscopy

► Results Halo Nuclei

3 Isotope Shift → Nuclear Charge Radius

► Charge radius – proton distribution ► Nuclear model – independent

Isotop 1 Δν Absorption IS spectra

Isotop 2

ΔνIS = ΔνMS + ΔνFS

4 Isotope Shift

ΔνIS = ΔνMS + ΔνFS meausrements calculations charge radius

≈10 GHz ≈1 MHz

► Calculations up to three e- system Be+

Z.-C. Yan et al., Phys. Rev. Lett., 100, 243002 (2008) M. Puchalski, K. Pachucki Phys. Rev A 78, 052511 (2008)

5 Isotope Shift

ΔνIS = ΔνMS + ΔνFS meausrements calculations charge radius

≈10 GHz ≈1 MHz

r 2 Δν = 2πZeΔ|ψ(0)|2 2 FS 3 δ r

V(r) field shift coefficient C - calculations Z.-C. Yan et al., Phys. Rev. Lett., 100, 243002 (2008) M. Puchalski, K. Pachucki Phys. Rev A 78, 052511 (2008)

6 6He, 8He

► 6He, 8He – isotope shifts measurements in magneto optical trap, Argonne National Lab, GANIL

P. Müller et al., Phys. Rev. Lett., 99, 252501 (2007)

L.-B. Wang et al., Phys. Rev. Lett., 93, 142501 (2004): 1.912(18) fm for He-6

7 Beryllium Measurements

8 Where did we measure?

RADIOACTIVE LABORATORY

1 GeV PROTONS ROBOT

►1GeV Proton Beam from PSB GPS Separator ►Uranium-Carbite Target CONTROL ROOM ►GPS Mass Separator REX-ISOLDE EXPERIMENTAL HALL

►COLLAPS Beam-Line COLLAPSBeam-Line

ISOLTRAP

9 Collinear Laser Spectroscopy

Ion Beam

► Laser Frequency is Fixed Ekin~60 keV

Deflection ► Doppler Tuning Deceleration Collinear + (Doppler-tuning) Laser Beam + Photomultipliers νc = ν0 ⋅ γ ⋅(1+ β) (Signal Detection)

acceleration voltage / kV

0 15 30 45 60

mvE 2 )2/( =δ=δ=δ constvmv Tk 22 v =δ eUm 10 Experimental Setup at COLLAPS

► Laser Frequency is Fixed Ion Beam ► Doppler Tuning Ekin~60 keV

Collinear Deflection Deceleration Laser Beam + (Doppler-tuning) + νc = ν0 ⋅ γ ⋅(1+ β) Photomultipliers (Signal Detection) ► Limitation – knowledge of ion velocity

2eU ΔU/U ≈ 10-4 β ≈ 2 ⇒ΔνIS ≈ 18 MHz 0cm IS (Be): 5-15 MHz

11 Two Laser Beams

Ion Beam Ekin~60 keV νc = ν0 ⋅ γ ⋅(1+ β)

Deflection Deceleration a = 0 ⋅γ⋅(1− βνν ) (Doppler-tuning) Collinear + 22 2 2 Laser Beam + νc ⋅ νa 0 (1 β ) ν=−⋅γ⋅ν= 0 νc = ν0 ⋅ γ ()1+⋅ β

Anti-collinear Laser Beam Photomultipliers (Signal Detection) ν a =ν 0 ⋅γ ⋅(1− β )

► Laser Frequency Measurement Δν/ν < 10-9 ► Dedicated laser system

12 Experimental Setup

Anti-collinear Laser Setup

Collinear Laser Setup

13 Laser Spectroscopy Setup

Anti-collinear Laser Setup

BBO

Collinear Laser Setup

BBO 14 Laser Spectroscopy Setup

15 Laser Spectroscopy Setup

16 Energy Level Scheme

17 2s1/2 –2p1/2 Transition

4500 7Be (D1 line) 4000

Fitting … 3500 ► Voigt Profile 3000 2500

2000 Counts/ s 1500

1000 1800 10Be (D1 line) 500 1600 -50 -40 -30 -20 -10 0 10 20 1400 150 11Be (D1 line) 1200 140 1000 800 130 Counts/ s 600 120 400 200 110 Counts/ s Counts/ 0 -100 -96 -92 -88 -84 -80 -76 100 Voltage [V] 90

-200 -175 -150 -125 -100 -75 -50 Voltage [V] Energy Level Scheme

19 2s1/2 –2p3/2 Transition

20 Nuclear Charge Radius

2 2πZe 2 2 δν = δνMS + Δ|ψ(0)| δ rc IS 3

δνFS

A ⎛ 922 ⎞ )Be( r )Be( = δ + rr ⎜ Be⎟ c cc ⎝ ⎠

9 rc = (12)2.519)Be( fm (Electron Scattering)

J. A. Jansen, Nuc. Phys. A, 188, 337-352, (1972).

21 Radius of one Neutron-Halo 11Be

Simple frozen core two-body model:

► 11Be consists of the 10Be core and halo-neutron

► Difference in proton distribution attributed to influence of the halo-neutron

classical picture:

2 112 102 centermass c −= rrR c )Be()Be(

10 center m )Be( of mass r R ⋅= halo−Neutron centermass m )Neutron(

22 Radius of one Neutron-Halo 11Be

► Pure center-of-mass motion

23 Radius of one Neutron-Halo 11Be

► Pure center-of-mass motion

► Additional contribution: Core polarization (intrinsic structure of 10Be)

Suggestion by I. Tanihata: Combine Charge- and Matter-Radii with B(E1) to disentangle core excitation from center-of-mass motion.

24 Conclusion & Outlook

Current status: ► Isotope shift of 7,9,10,11Be+ determined with ~ 1 MHz precision ► Determination of charge radii with ~1% uncertainty

Near Future: ► Isotope shift measurement of 12Be using collinear laser spectroscopy with an improved detection system

25 Thank You for Attention

Beam-time Crew

26 Beryllium ion production • RILIS (ISOLDE laser ion source)

Isotope Half life Yield (ions/μC) auto-ionizing state 7 21 Be 53.12 d 1.4E+10 2p S0

10Be 1.51E+6 a 6.0E+09 IP ~ 9 eV

11Be 13.8 s 7.0E+06 297.3 nm 12Be 23.6 ms 1.5E+03 2s2p 1P 14Be 4.35 ms 4.0E+00 1

234.9 nm

21 2s S0 Efficiency: ~ 7 %

27 Commercial Frequency Comb

28