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Euroschool on Physics with Exotic Beams, Mainz 2005
LectureLecture SeriesSeries::Atomic PhysicsAtomic Physics Tools inTools in
Nuclear PhysicsNuclear PhysicsIII.III. Recent Laserspectroscopic ResultsRecent Laserspectroscopic Results
Klaus BlaumKlaus BlaumJohannes GutenbergJohannes Gutenberg--University MainzUniversity Mainz
and GSI Darmstadt, Germanyand GSI Darmstadt, Germany
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OutlineOutline
1. Collinear laser spectroscopy (COLLAPS, IGISOL)
2. Atom trap laser spectroscopy (ATTA)
3. Resonance laser spectroscopy (ToPLiS)
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COLLAPS SetupCOLLAPS Setup
Collinear laser spectroscopy with resonance ionization detection
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The Collinear PrincipleThe Collinear Principle
“Collinear” ⇒ Superposition of laser and fast atom-/ion beam
“fast beam” (ISOLDE: Ukin(Ionen)=60 keV):
⇒Doppler shift of the usedtransition in neon about 1.2 THz
Energy spread of the ions is constant in acceleration ⇒ Compression of the velocity distribution in beam direction:
⇒ Energy spread in beam direction: δE < 50 µeV ≈ 0.5 K
Doppler shift ⇒ laser at fixed frequency and “Doppler tuning”, i.e. Scan of the velocity of the ions
220Doppler mcUe2
11
≅ββ−β±
×ν=ν ,
UemTkvconstvmvmvE
2)(
222
21 =⇒=== δδδδ
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Optical Excitation SchemeOptical Excitation Scheme of Neof Ne0 1 2
J
3s’[1/2]0
2p6 1S0
3s’[1/2]1
3s[3/2]1 3s[3/2]2
3p[3/2]2
3p[3/2]1
12.2%
∆Eion Na+
λ = 614.47 nm
-2
-4
-6
-20
-22
Ne*
3s’[1/2]0
2p6 1S0
3s’[1/2]1
3s[3/2]1 3s[3/2]2
3p[3/2]2
3p[3/2]1
12.2%
∆Eion Na+
λ = 614.47 nm
-2
-4
-6
-20
-22
Ne*
Charge exchange at Na → metastable state
opt. pumping in the ground state
Collision with chlorine gas: Utilization of differentionisation energies out of the meta stablestate and ground state
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HFS and ISHFS and IS MeasurementsMeasurements
Collis.ionization
Ions
Atoms
63750 63800 63850 63900 63950 640000.090
0.095
0.100
0.105
0.110
0.115
0.120
63750 63800 63850 63900 63950 640000.090
0.095
0.100
0.105
0.110
0.115
0.120
Nor
mat
edSi
gnal
7x105
8x105
9x105
1x106
1x106
Ato
m-S
igna
l
9x104
1x105
1x105
1x105
1x105
1x105
2x105
Ione
n-Si
gnal
19Ne
⇒ decisive increase in sensitivity:
Measurement on 28Ne with 45 Ions / ISOLDE pulse
⇒ 5 hours of data taking per spectrum
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ChargeCharge RadiiRadii:: TheoryTheory and Experimentand Experiment
Collaps upper limitCollaps lower limitFinite range Droplet
Ne
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LaserspectroscopyLaserspectroscopy at IGISOL / Jyväskyläat IGISOL / Jyväskylä
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
IGISOL: E ~40 keV, δE ~100 eV
DC-cooler: E~ 40 keV, δ E < 1 eVtransmission > 60%
Buncher: Accumulation time 10 ms -10 s(typically 100 ms - 1 s)bunch length 15 µs (FWHM)
Bunching for collinear laser spectroscopy:
A. Nieminen et al.,Phys. Rev. Lett. 88 (2002)
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Bunching for Collinear LaserspectroscopyBunching for Collinear Laserspectroscopy
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Preparation TechniquePreparation Technique: Laser Ion: Laser Ion Source TrapSource Trap
Principle: RFQ Trap and Laser System
efficient and highly-selective (R > 105) production of exotic ionspreparation of cleaned, cooled, and bunched beams with low emittanceproduction of polarized radioactive ion beams by optical pumpingfirst demonstration of cooled and pulsed beam release in Mainz (2004)
Goals and Results
Ti:Sa 1
Ti:Sa 2
Ti:Sa 3
Nd:YAG
Ion Beam
Gas filledRFQ Trap
Ion Repeller
to on-lineExperiments
Laser-beams
Ion Source HV Platform
Atom source
60 KV Mass separator Laser System
K. Wendt et al., Nucl. Phys. A 746, 47c (2004)
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Status in 2003: ChargeStatus in 2003: Charge RadiiRadii of He and Liof He and Li--IsotopesIsotopes
3He∞
1/2+
4He∞0+
6He807 ms
0+
8He119 ms
0+
3He∞
1/2+
4He∞0+
6He807 ms
0+
8He119 ms
0+
Shiner et al.PRL 18, 3553 (1995),Laser spectroscopy in an atomic beam
G. Carboni et al.Nucl. Phys. A, 278,381 (1977)Laser Spectroscopy of muonic helium
6Li∞1+
7Li∞
3/2-
8Li838 ms
2+
9Li178 ms
3/2-
11Li8.5 ms
3/2-
6Li∞1+
7Li∞
3/2-
8Li838 ms
2+
9Li178 ms
3/2-
11Li8.5 ms
3/2-
Riis et al.PRA 49, 207 (1994)Laser spectroscopy of helium-like lithium
2rδ
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Courtesy of Peter Müller,Argonne Nat. Lab
66He He –– Single AtomSingle Atom SpectroscopySpectroscopy
Photoncounter
Zeemans lower
MOT
Transversecooling
389 nm 1083 nm
Atom Trapping of 6He
6Hetrapping rate
~ 2 / min
Photoncounter
Zeemans lower
MOT
Transversecooling
389 nm 1083 nm
Atom Trapping of 6He
6Hetrapping rate
~ 2 / min
0 5 10 15 200.0
0.2
0.4
0.6
0.8
1.0
1.2
Pho
ton
coun
trate
/ kH
z
Time (s)-8 -6 -4 -2 0 2 4 6 8
50
100
150
200
250
300
Frequency (MHz)
Pho
ton
coun
ts
Single atom signal
One 6He atom
6He spectroscopy
~150 6Hein 1 hr
0 5 10 15 200.0
0.2
0.4
0.6
0.8
1.0
1.2
Pho
ton
coun
trate
/ kH
z
Time (s)-8 -6 -4 -2 0 2 4 6 8
50
100
150
200
250
300
Frequency (MHz)
Pho
ton
coun
ts
Single atom signal
One 6He atom
6He spectroscopy
~150 6Hein 1 hr
RF -Discharge
Krcarrier
gas
He*
Spectroscopy389 nm
2 3S1
1 1S0
2 3P2
3 3P2
Trap1083 nm
He level scheme
RF -Discharge
Krcarrier
gas
He*
RF -Discharge
Krcarrier
gas
He*
Spectroscopy389 nm
2 3S1
1 1S0
2 3P2
3 3P2
Trap1083 nm
He level scheme
Spectroscopy389 nm
2 3S1
1 1S0
2 3P2
3 3P2
Trap1083 nm
He level scheme
6He
7Li3+
60 MeV
6He Production @ ATLAS
Graphite
~ 1×106 / s
6He
7Li3+
60 MeV
6He Production @ ATLAS
Graphite
~ 1×106 / s
6He
7Li3+
60 MeV
6He Production @ ATLAS
Graphite
~ 1×106 / s
6He
7Li3+
60 MeV
6He Production @ ATLAS
Graphite
~ 1×106 / s
L.-B. Wang et al., PRL 93, 142501 (2004)
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66He He –– NuclearNuclear Charge RadiusCharge Radius
Isotope shift(23S1 - 33P2, 6He – 4He)
43 194.772(56) MHz
6He rms charge radius
2.054(14) fm (0.7%)
L.-B. Wang et al.,PRL 93, 142501 (2004)
1.7 1.8 1.9 2.0 2.1 Point-Proton Radius of He-6 (fm)
He-6
Reaction collision
Elastic collision
Atomic isotope shift
Cluster models
No-core shell model
Quantum MC
Modelindependent!
Exp
erim
ent
Theo
ry
Tanihata ‘92
Alkhazov ‘97
This work
Csoto ‘93
Funada ‘94
Varga ‘94
Wurzer ‘97
Esbensen ‘97
Navratil ‘01
Pieper ‘04
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Resonance IonizationResonance Ionization of LithiumCourtesy W. Nörtershäuser GSI Darmstadt of Lithium
2s 2S1/2
3s 2S1/2
2p 2P1/2,3/2
3d 2D3/2,5/2τ = 30 ns
2 × 735 nm
610 nm
5.3917 eV2s – 3s transition→ Narrow line2-photon spectroscopy→ Doppler cancellation
“Doubly-Resonant-4-Photon Ionization”
Spontaneous decay→ Decoupling of precise
spectroscopy and efficient ionization
2p – 3d transition → Resonance enhancement
for efficient ionization
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SetupSetup forfor LithiumLithium MeasurementsMeasurements ((ToPLiSToPLiS))
Ti:Sa Laser735 nm
Dye Laser 610 nm
ElectrostaticLenses
PZT
CO -Laser2
Comparison
Serv
o
RF Generator
Reference Diode Laser I2
Servo
Reaction Products
Surface Ion Source
Magnet
Servo
Servo
W Target
Ion Signal
6,7,8,9,11Li
Ti:Sa Laser735 nm
Dye Laser 610 nm
ElectrostaticLenses
PZT
CO -Laser2
Comparison
Serv
o
RF Generator
Reference Diode Laser I2
Servo
Reaction Products
Surface Ion Source
Magnet
Servo
Servo
W Target
Ion Signal
6,7,8,9,11Li
• 8,9,11Li all have half-life < 1 s: must be studied at accelerator online mass separator facilities
• Use thin (~300 nm) heated carbon foils to catch ions, neutralize, and rapidly release neutral atoms
• Use resonant enhancement cavity to efficiently drive two-photon transitions
• Use beat-frequency methods for reliable and precise control of resonant laser
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77Li LineLi Line ShapeShape
5000 5500 6000 6500 7000100
101
102
103
104
Cou
nts
DL/TiSa - Beat Frequency (MHz)
F=1
→F=
1
F=2
→F=
2 7LiLinewidth Voigt
ΓL= 4.6 (1) MHz (FWHM)ΓG= 1.8 (1) MHz (FW 1/e)
Expected Natural WidthΓL= 2.7 MHz (FWHM)
Background Gaussian ΓG ≈ 1.2 GHzrelative Amplitude ≈ 3 × 10-3
Amplitude RatioF=1 : F=2 2.85 : 5
F =2F = 1
F= 2
F= 12S1/2
3S1/2
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1111LiLi ResonanceResonance
6360 6370 6380 6710 6720 67300
50
100
150
200
Cou
nts
/ 50
s
Beat Frequency (MHz)
F= 2F= 1
F= 2
F= 12S1/2
3S1/2
F =
1 →
F =
1
F =
2 →
F =
2 11LiProduction Rate:30,000 /sLifetime:8.5 ms !
F= 2F= 1
F= 2
F= 12S1/2
3S1/2
F =
1 →
F =
1
F =
2 →
F =
2 11LiProduction Rate:30,000 /sLifetime:8.5 ms !
21 85
83 ννν11
cg +=
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ChargeCharge RadiiRadii of Lithiumof Lithium IsotopesIsotopes
6 7 8 9 10 11
2.1
2.2
2.3
2.4
2.5
2.6
2.7 This Tan85 LBSM SVMC DCM AV18IL2 NCSM FMD
r c (fm
)
Li Isotope
EXPERIMENTInteraction Cross Section(Tanihata, 1985)
TOPLIS, Isotope Shift(GSI + TRIUMF 2004)
THEORYGFMC–AV18IL2(Pieper, Wiringa 2001/02)
SVMC (Suzuki 2002)
LBSM (Navratil 1998/2003)
DCM (Tomaselli 2002)
FMD (Neff, priv. comm.)++
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LaserLaser SpectroscopySpectroscopy inin thethe Chart ofChart of NuclidesNuclides
2 8
20
28
20
20-31Na
36-47K
39-50Ca
2
8
32-40,46Ar
17-28Ne
5044,45Ti
28
11Be6-11Li
Exclusive approach for a model-independent <r2> determination of short-lived nuclei !
170-178Hf161-179Lu
200-210Po
101-110Ag
82
126
152
82
72-96Kr
76-98Rb
77-100Sr
102-120Cd
104-127In
108-132Sn
116-146Xe
118-146Cs
132-150Nd
138-154Sm
138-159Eu
146-165Dy
151-165Ho
150-167Er153-172Tm
153-176Yb
178-198Pt
183-197Au181-206Hg
185-214Pb
202-213Bi
207-228Fr208-232Ra
187-208Tl
202-225Rn
182-193Ir
240-244Am
227Ac232Th
235-238U
237Np
238-244Pu
249Cf249Bk
254Es
248Cm
50
147-159Tb
120-148Ba
255Fm
146-160Gd
87-102Zr
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LaSpecLaSpec at NUSTAR / FAIRat NUSTAR / FAIR
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SummarySummary ofof LectureLecture IIIIII
•• Laser Spectroscopy of fewLaser Spectroscopy of few--electron systems combined with precise electron systems combined with precise atomic physics calculations can provide accurate atomic physics calculations can provide accurate rmsrms charge radii.charge radii.
•• This method was previously used for charge radii determination oThis method was previously used for charge radii determination of f stable isotopes (H, He, Hestable isotopes (H, He, He--like Lithium).like Lithium).
•• First measurements on light shortFirst measurements on light short--lived nuclei were performed.lived nuclei were performed.
•• ModelModel--independent charge radii of halo nuclei (independent charge radii of halo nuclei (66He, He, 1111Li) were Li) were obtained for the first time.obtained for the first time.
• Discrimination of nuclear models • Better understanding of nuclear structure and
nucleon–nucleon interactions
Thanks a lot foryour attention.