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

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

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

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

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

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+

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)

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

Image by P.O. Schmidt

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)

• 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+

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

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!

• 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

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

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)

.

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)

Level crossings: optical transitions

neutral hydrogen-like

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+

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

EBIT fluorescence spectroscopy

Orts et al., PRA 76, 052501 (2007) Orts et al., PRL 97, 103002 (2006)

193Ir17+

• 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

EBIT fluorescence spectroscopy

• Line identification by scanning electron beam energy

• Information in substructures

Figures: Alex Windberger, Hendrik Bekker

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.

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