Precision Molecular Ion Spectroscopy:

A New Probe for New Physics

Brian Odom

milliKelvin Molecular Ion Research

… a few years ago

Stephan SchillerDusseldorf

Michael DrewsenAarhus

milliKelvin Molecular Ion Research

Stephan SchillerDusseldorf

Michael DrewsenAarhus

Ike ChuangMIT

Eric HudsonUCLA

Brian OdomNorthwestern

Ken BrownGeorgia Tech

… today

Tobias SchaetzMPI-Garching

Stephan WillitschBasel

Piet SchmidtPTB

Zhang Chaobo Nanyang

Kunihiro Okada Tokyo

Yoshiki MoriwakiToyama

Precision AMO Spectroscopy ( for the “m”)

Atomic optical spectroscopy

Best molecular spectroscopy

Atomic microwave spectroscopy

Why are Molecules so Far Behind?

Why cycle?• Laser cooling• Single atom detection

Atoms are easy …molecules are hard

HEP-Inspired Molecular Possibilities

p+

e-

Parity violation at molecular level

Time-variation of constants

Molecular enhancementDeMille, et al, PRL 100, 023003 (2008)

Nuclear spin-dependent (NSD) parity violation

1-sigma constraints on PNC meson couplingsHaxton et al, Phys Rev C 65 045502

Fundamental electric dipole moments

Time-Varying Constants

• Possibilities:• Continuing variation in time • “Phase-shift” behavior• Variation with space, not time• Variation with matter density, not time

• We cannot predict rate or type of variation, but…

(30 40)

Is this even possible?Kaluza-Klein, string theories allow/predict variations.

What are the predictions?

electron-proton mass ratio mfine structure constant a

Units Ain’t Welcome In These Parts

+

-

Experiment: Count the Cs clock ticks for a photon to cross H atom

Conclusion: 1 s defined by Cs, c is defined…so rH is changing

Say that number changes from year to year…

But…if 1 m were defined by rH , c still defined, we conclude that wCs is changing

Talk of unitful constants changing obscures the physics

Cs

What Does This Have to Do with Dark Energy?

?

Strategies for a Hard ProblemStrategy 1: The denominator approach D / m m ≈ 10-6, T ≈ 109 years

Data from Ultraviolet and Visible Echelle Spectrograph mounted on the Very Large Telescope of the European Southern Observatory Ubachs, Buning, Eikemma, and Reinhold, J Molec. Spect. 241, 155 (2007)

T

Strategy 2: The numerator approach T ≈ 1 year… D / m m < 10-15 ???

State of unConstant Affairs

Quasar absorption lines:

176 10 / yr

1764 (14) 10 / yr

Al+/ Hg+ clock comparison: 173.9 10 / yr

Quasar absorption lines:151.7 (0.5) 10 / yr

Ubachs, Buning, Eikemma, and Reinhold,J Molec. Spect. 241, 155 (2007)

150.3 10 / yr

H2:

NH3 / (CO, HCO+, HCN):Henkel et al, Astronomy and Astrophysics 440, 893 (2005)Combes and Wiklind, Astrophys J 486, L79 (1997)

a

mLaboratory: 1565 10 / yr

Chardonnet, http://www.ptb.de/ACFC2007/present.htm SF6 :

Laboratory:

m is way behind … because it needs molecules!

Molecular Degeneracy Can Help

Some systematics, such as clock instability or Doppler shift, impose fractional frequency error

Molecular complexity is definitely a good thing here

Ba+ Laser Cooling

Why Barium?• Heavy (effective sympathetic cooling of heavy molecular ions)• Cooling transition is most red option

Our First Ion Trap

Fluorescence Images of Trapped Ba+

• At low enough temperature (~ 0.1 K) crystallization occurs• Ba-138 is pushed left by light pressure

Trapped Barium Coulomb Crystals

… and Throw in Some Molecular Ions

(Following Drewsen at Aarhus and Schiller at Dusseldorf)

Ba+ fluorescing ions

BaH+ dark ions,

(probably

milliKelvin!)

Loading SiO+

First ablate Ba

target

Then ablate SiO

target

Quantum Logic Spectroscopy,

State ReadoutWorld’s best spectroscopy (QLS) is on a non-laser cooled ion…Why not on a molecular ion?

Internal state

Motional state

n=1n=0

n=1n=0

Spectroscopy ion

Logic ion

?

Spectroscopy ion is hard to read out, but logic ion is easy

Internal state

Motional state

n=1n=0

n=1n=0

Spectroscopy ion

Logic ion

Quantum Logic Spectroscopy,

State TransferWorld’s best spectroscopy (QLS) is on a non-laser cooled ion…Why not on a molecular ion?

Spectroscopy ion is hard to read out, but logic ion is easy

mQLS Trap Design

3 mm

mQLS Table and Trap

mQLS Vacuum Chamber Assembly

The People Doing the WorkPostdocsJoan MarlerJason Nguyen

Grad StudentsChien-Yu LienYen-Wei LinVaishnavi RajagopalChris SeckDavid TaborMing-Feng Tu

UndergradsMarc BourgeoisGreg McGlynnIngrid RinglerLauren RuthScott Williams

… and The People Paying for ItIGERTQuantum Coherent Optical and Matter Systems

Extras…

Sounds Great.What’s the

Catch?

Rotational Cooling of Hydrides

Schiller and Drewsen groups (2010)

What would still be nice?• Faster cooling• Applicable to heavier species

Cool Rotations into Electronic Excitation?

We would like diagonal Franck Condon Factors

Femtosecond Pulse Shaping

1 cm-1 resolution currently achieved

Pulse-Shaping for AlH+ Rotational Cooling

Current resolution is sufficient for cooling

Simulation of AlH+ Rotational Cooling

Expect ~7 ms cooling timescale (compare with 10 s timescale of vibrational excitation technique)

Review: Radiofrequency Ion Traps

http://www.exphy.uni-duesseldorf.de/ResearchInst

~ 5 mm +

+- -

Review: Radiofrequency Ion Traps

http://www.exphy.uni-duesseldorf.de/ResearchInst

~ 5 mm -

-+ +