Nuclear charge radius determination
of the halo nucleus Be-11
Monika Žáková, Johannes Gutenberg-Universität Mainz
M. Bissell6, K. Blaum7, Ch. Geppert2, M. Kowalska3, J. Krämer1 , A. Krieger1, R. Neugart1, W.
Nörtershäuser1,2 , R. Sanchez1, F. Schmidt-Kaler4, D. Tiedemann1, D. Yordanov7, C. Zimmermann5
Johannes Gutenberg-Universität Mainz, Germany
Darmstadt, Germany
3 CERN
4 Universität Ulm, Germany
5 Eberhard-Karls Universität Tübingen, Germany
6 Instituut voor Kern- en Stralingsfysica, Leuven
7Max Planck Institut für Kernphysik, Heidelberg
1
2 GSI
Laser Spectroscopy of Highly Charged
Ions and Exotic Radioactive Nuclei
(Helmholtz Young Investigators Group)
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
ΔνIS
Absorption
spectra
Isotop 2
ΔνIS = ΔνMS + ΔνFS
4
Isotope Shift
ΔνIS =
meausrements
ΔνMS + ΔνFS
calculations
≈10 GHz
charge radius
≈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 =
meausrements
ΔνMS + ΔνFS
calculations
≈10 GHz
charge radius
≈1 MHz
r
r
2
V(r)
2
2πZe
ΔνFS=
Δ|ψ(0)|2 δ
3
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
p
S
GP
►Uranium-Carbite Target
►GPS Mass Separator
Se
r
to
a
ar
CONTROL
ROOM
REX-ISOLDE
EXPERIMENTAL HALL
►COLLAPS Beam-Line
COLLAPS Beam-Line
ISOLTRAP
9
Collinear Laser Spectroscopy
Ion Beam
Ekin~60 keV
► Laser Frequency is Fixed
Deflection Deceleration
► Doppler Tuning
Collinear
Laser Beam
ν c = ν 0 ⋅ γ ⋅ (1 + β )
+
(Doppler-tuning)
+
Photomultipliers
(Signal Detection)
acceleration voltage / kV
0
15
30
45
60
δE = δ(mv 2 / 2) = mv δv = const
k 2T 2
δv =
eUm
10
Experimental Setup at COLLAPS
► Laser Frequency is Fixed
Ion Beam
Ekin~60 keV
► Doppler Tuning
Collinear
Laser Beam
Deflection Deceleration
ν c = ν 0 ⋅ γ ⋅ (1 + β )
+
(Doppler-tuning)
+
Photomultipliers
(Signal Detection)
► Limitation – knowledge of ion velocity
2eU
β≈
m0 c 2
ΔU/U ≈ 10-4
⇒ ΔνIS ≈ 18 MHz
IS (Be): 5-15 MHz
11
Two Laser Beams
ν c = ν 0 ⋅ γ ⋅ (1 + β )
Ion Beam
Ekin~60 keV
Deflection Deceleration
Collinear
Laser Beam
+
ν c = ν 0 ⋅ γ ⋅ (1 + β )
(Doppler-tuning)
+
νa = ν0 ⋅ γ ⋅ (1 − β )
(
)
2
2
2
2
=
ν
⋅
γ
⋅
1
−
β
=
ν
ν c ⋅ νa
0
0
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
7
Be (D1 line)
4000
Fitting …
3500
Counts/ s
► Voigt Profile
3000
2500
2000
1500
1800
1000
10
Be (D1 line)
500
1600
-50
150
11
1200
800
-30
-20
-10
0
10
20
Be (D1 line)
130
600
400
200
0
-100
-40
140
1000
Counts/ s
Counts/ s
1400
-96
-92
-88
-84
Voltage [V]
-80
-76
120
110
100
90
-200
-175
-150
-125
Voltage [V]
-100
-75
-50
Energy Level Scheme
19
2s1/2 – 2p3/2 Transition
20
Nuclear Charge Radius
δνIS =
δνMS
2
2πZe
+
Δ|ψ(0)|2 δ rc 2
3
δνFS
rc ( A Be) = δ rc2 + rc2 ⎛⎜⎝ 9 Be ⎞⎟⎠
rc (9 Be) = 2.519 (12) 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
Rcentermass
= rc2 (11 Be) − rc2 (10 Be)
rhalo− Neutron = Rcentermass ⋅
10
m( Be)
m( Neutron )
center
of mass
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)
7Be
53.12 d
1.4E+10
10Be
1.51E+6 a
6.0E+09
11Be
13.8 s
7.0E+06
12Be
23.6 ms
1.5E+03
14Be
4.35 ms
4.0E+00
auto-ionizing state
2p2 1S0
IP ~ 9 eV
297.3 nm
2s2p 1P1
234.9 nm
2s2 1S0
Efficiency: ~ 7 %
27
Commercial Frequency Comb
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