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Investigating α time variation with cold highly charged ions
Oscar O. Versolato
Max-Planck-Institut für Kernphysik, D-69117 Heidelberg
Experimental Few-Particle Quantum Dynamics
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The collaboration
Highly charged ions
Electron beam ion traps (EBITs)
EBIT spectroscopy
Coulomb crystals
Linear Paul trap design
Molecular ions
Quantum logic readout
High-accuracy clocks
Frequency comb
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Overview
• Highly charged ions for metrology and fundamental physics
• Cryogenic Paul trap for sympathetic cooling of HCIs
• Ir17+ and time variation of fine structure constant
• Outlook
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Highly charged ions, scaling laws
• Ionization energy ~ Z2 • Fine structure ~ Z4
• Bohr radius ~ Z-1; electron density at nucleus ~ Z3 • Weak matrix element (parity violation) ~ Z5
• QED contributions ~ (Zα)n
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Laser spectroscopy of HCIs
Ar13+ 2P3/2–2P1/2 @ 441 nm by pulsed dye laser
Evaporatively cooled from 240 to 28eV (12eV achieved!)
Accuracy: 220MHz, linewidth 28pm/43GHz (!) (natural: 111Hz)
Laser
π1/2+
π3/2+
π1/2-
π3/2-
V. Mäckel, et al., PRL. 107, 143002 (2011)
Limited by Doppler line width! Need cooling…
K. Schnorr et al., in preparation
105 K
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Sympathetic Cooling of HCIs • RETRAP (LLNL):
cryogenic Penning trap
Be+ cools Xe34+
L. Gruber et al., PRL 86, 636 (2001)
P L. Gruber et al., Physica Scripta. 71, (2005)
• Proposals: M. Bussmann et al., Int. J. Mass Spectr. 251, 179 (2006)
M. Bussmann et al., Hyperfine Interact. 173, 27–34 (2007)
• SPECTRAP @ GSI
Resistive cooling & 24Mg+ ion cloud laser cooled in Penning trap
R. Cazan et al., Hyperfine Interact. 196, 177–189 (2010)
Z. Andelkovic, arXiv:1211.2106 (2012)
Xe34+
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Sympathetic Cooling of HCIs
Coulomb crystal
2 single-ion Coulomb crystal
- Can store many ions - Temp. < 100mK (compare: 105K!) …micromotion - Be+ as sympathetic coolant; optimal q/m
- Only 1 HCI for highest accuracy - Need quantum logic readout
in a Paul trap
P. F. Staanum, (Michael Drewsen) et al. , Nature Physics 6 (2010)
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Sympathetic Cooling of HCIs in a cryogenic Paul trap
• Cryogenic linear Paul trap at T=4K • Injection of HCIs from EBIT at MPIK • Sympathetic cooling of HCIs with Be+ • Quantum logic readout with PTB for highest accuracy
MPIK & Aarhus
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Image by P.O. Schmidt
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Cryogenic Paul Trap Experiments A cryogenic linear RF ion trap for sympathetic laser cooling of HCIs
and molecular ions
M. Schwarz, et al., Rev. Sci. Instr. 83 (2012)
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• UHV vacuum < 10-14 mbar (H2@ 4K) • Low exposure to 300K blackbody fields • Plentiful optical access ports • Commissioned with Mg+ and MgH+ in Aarhus (Michael Drewsen‘s Ion Trap group)
Cryogenic Paul Trap Experiments A cryogenic linear RF ion trap for sympathetic laser cooling of HCIs
and molecular ions
Mg+ MgH+
MgH+
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Experiments with cooled MgH+ intermezzo
Preparing externally and internally ultra-cold molecular ions with the Ion Trap Group at Aarhus University
Experiment with exciting results. Stay tuned...
P. F. Staanum et al., Nature Physics 6 (2010)
Rotational state distribution
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Sikler lens
Einzel lens 1
90 electrostatic quadrupole deflector
Einzel lens 2
retardation electrode
beam diagnostic 1 beam diagnostic 2
to CryPTEx
ion beam from EBIT
Laser
x/y deflector
pulsed drift cavity
Time focusing
Extr. and injection beamline*
*Slide by Lisa Schmöger
Last week: First extraction and deceleration!
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• 2-photon photo-ionization of Be for loading (2 x SHG).
• Broad range laser system with narrow linewidth based on Ti:Sa laser and SHG systems for HCI spectroscopy.
Be+ laser systems
Eion= 9.3 eV
235nm
235nm
9Be 2s2 1S0
2s2p 1P1
9Be+ 2s 2S1/2
2p 2P3/2 2p 2P1/2
313nm
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Highly charged ions for metrology
• Strongly bound electrons
• Low susceptibility to certain external field shifts:
- Second order Zeeman shift
~ 1/Zh2 (BUT: linear shift ~MHz/G)
- Stark shifts (BBR, light shift, trap induced, quadrupole)
BBR ~ 1/Za4
Makes for high-accuracy atomic clock
Derevianko et al. PRL 109 (2012) Schiller, PRL 98 (2007) 10-19 or 10-100x better
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Variation of alpha
• Quasar absorption spectra – “Australian dipole” at 4σ
– α/ α ~ 10-19/year
• Hg+/Al+ Atomic clocks – -1.6(2.3) x 10-17/year
– Need 100x improvement!
Webb et al., PRL 107, 191101 (2011) Berengut et al, Europhys. Lett. 97, 20006 (2012)
Rosenband et al., Science 319 (2008)
.
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Highly charged ions for α-dot
Strong relativistic effects, enhanced sensitivity:
• High nuclear charge Z
• High ionization potential In
• Differences in the configuration composition (i.e. ν, j)
• Scaling even faster with hole transitions
BUT: need to keep transitions in optical regime…
Berengut et al., PRL 106, 210802 (2011)
Berengut et al., PRL 105, 120801 (2010)
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Level crossings: optical transitions
neutral hydrogen-like
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Level crossings: optical transitions
Sm14+
Berengut et al., PRL 105, 120801 (2010)
Berengut et al., PRL 106, 210802 (2011)
Ir17+
Berengut et al., arXiv:1204.0603v1 (2012)
Cf16+
q ~ 140,000 cm-1
q ~ 370,000 cm-1
q ~ 450,000 cm-1
Compare: Hg+ at
q ~ 52,200 cm-1 Berengut et al., PRL 106, 210802 (2011)
Ir17+
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193Ir17+ partial level structure
4f 5s F13 3 0
3
4f 5s F13 3 0
4
4f 5s F13 3 0
2
4f 5s F13 1 0
3
4f 5s H12 2 3
6
4f S14 1
0
4f 5s F12 2 3
4
F=3/2
F=11/2
F=7/2F=5/2
F=9/2
even parityodd parity
0
4838
26272
31492
5055
35285
45214E (cm
-1)
1980 nm
q=-385,000 cm-1
283+27-23 nm
q=367,000 cm-1
q=24,183 cm-1
471 nm
I=3/2 Δq≈730,000 cm-1
Accuracy of calculation: 6000 cm-1
*Slide courtesy of P.O. Schmidt
*
221 nm
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EBIT fluorescence spectroscopy
Orts et al., PRA 76, 052501 (2007) Orts et al., PRL 97, 103002 (2006)
193Ir17+
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• Electron impact excites all levels • Observe fluorescent decay with grating spectrometer and CCD
• 200-750nm range observable • sub-ppm accuracy obtainable
4f125s2 3P1
4f125s2 3P0 4f125s2 1J6
4f125s2 1D2
4f125s2 3H4
4f125s2 3F3
4f125s2 1G4 4f125s2 3F2
4f125s2 3H5
4f125s2 3F4
4f125s2 3H6
4f14 1S0
4f135s 3F4
4f135s 3F3
4f135s 3F2
4f135s 1F3
221
283
248
471 318
2066
375 461
90 95
E1 E2 M1 M2
EBIT fluorescence spectroscopy
193Ir17+
237
270
219
267
Ti-like Ir55+
Figure: Alex Windberger
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EBIT fluorescence spectroscopy
• Line identification by scanning electron beam energy
• Information in substructures
Figures: Alex Windberger, Hendrik Bekker
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Summary & Outlook • Highly charged ions for metrology and fundamental physics. • Cryogenic Paul commissioned with MgH+ at Aarhus University
• Ir17+ excellent candidate. EBIT spectroscopy underway. • Be+ cooling laser system operational. Construction of PI and spectroscopy lasers underway at PTB.
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Experiment\MPIK • M. Schwarz
• A. Windberger
• L. Schmöger
• S. Bieling • O. O. Versolato
• J. Ullrich
• J. Crespo López-Urrutia
Experiment\Aarhus University • S. B. Kristensen
• A. Hansen
• A. D. Gingell
• L. Klosowski
• M. Drewsen
Experiment\PTB • P. O. Schmidt (PTB)
• J. Ullrich
Funding • MPG
• Aarhus University
• PTB
• COST-IOTA STSM
The crew & acknowledgements