P. Cheinet, B. Pelle, R. Faoro, A. Zuliani and P. Pillet Laboratoire Aimé Cotton, Orsay (France)...

P. Cheinet, B. Pelle, R. Faoro, A. Zuliani and P. Pillet

Laboratoire Aimé Cotton, Orsay (France)

Cold Rydberg atoms Cold Rydberg atoms

in Laboratoire Aimé Cottonin Laboratoire Aimé Cotton

04/12/201304/12/2013

2Cold Rydberg atoms in LAC04/12/13 Orsay

OutlineOutline

• Introduction: – Rydberg atoms and their

properties

• Cold cesium experiment

• A new experiment on Ytterbium

3Cold Rydberg atoms in LAC04/12/13 Orsay

Introduction: Rydberg Introduction: Rydberg atomatom

• Rydberg atom = highly excited atom

e-

Coolinglevels

|r>

|e>

|f>

E=-1/2n2Rydberg

levels

Failed screening at the core imply quantum defects

Most weight at large r!

1 10 100

-0,2

-0,1

0,0

0,1

0,2

Ene

rgy

or A

mpl

itude

Radius (a.u.)

Potential

23p e- Wavefunction

4Cold Rydberg atoms in LAC04/12/13 Orsay

1 10 100

-0,2

-0,1

0,0

0,1

0,2

Ene

rgy

or A

mpl

itude

Radius (a.u.)

E-field perturbed potential Unperturbed potential e- Wavefunction

Introduction: Rydberg Introduction: Rydberg atomatom

Zimmerman et al. 1979

Ionization

5Cold Rydberg atoms in LAC04/12/13 Orsay

Introduction: Rydberg Introduction: Rydberg atomatom

0 50 100 150 200-310

-300

-290

-280

-270

Ene

rgy

(cm

-1)

Field (V/cm)

23p3/2

23s

24s

Resonant energy transfer!@ ≈ 80V/cm

ssp 2423232 2/3

6Cold Rydberg atoms in LAC04/12/13 Orsay

Introduction: MotivationsIntroduction: Motivations

→ Possibility to tune interaction type and strength over ORDERS OF MAGNITUDE

→ Selective Field Ionisation (SFI) TOF

→ Many studies:→Dipole blocade→Few and many-body physics→Ultra-cold plasma→2 electron systems

7Cold Rydberg atoms in LAC04/12/13 Orsay

Cs experiment

8Cold Rydberg atoms in LAC04/12/13 Orsay

Experimental setupExperimental setup

• Sequence=MOT,Rydberg,delay,ionisation

Ions extracted throughthe 2 holes to the MCP

Up to 5kV ramp applied between

the 2 central grids

MCP

Delay = 1.5μs (frozen!)Then TOF recorded on MCP

9Cold Rydberg atoms in LAC04/12/13 Orsay

Cs exper./ 4-body Cs exper./ 4-body interactioninteraction

• Two close Förster resonances:→ @ ≈ 79.95V/cm→ @ ≈ 80.4V/cm (quasi-forbidden!)

• A 4-body exchange should be close…

ssp 2423232 2/3

2/52/1 2323242 dps

2/52/3 2323 dp

0 50 100 150 200-310

-300

-290

-280

-270

-260

-250

Ene

rgy

(cm

-1)

Field (V/cm)

23p3/2

23s

24s

23p1/2

23d5/2 TOF!d state is a signatureof 4-body

energy transfer!

10Cold Rydberg atoms in LAC04/12/13 Orsay

Cs exper./ 4-body Cs exper./ 4-body interactioninteraction

• Two close Förster resonances:→ @ ≈ 79.95V/cm→ @ ≈ 80.4V/cm (quasi-forbidden!)

• A 4-body exchange should be close…

ssp 2423232 2/3

2/52/1 2323242 dps

2/52/3 2323 dp

11Cold Rydberg atoms in LAC04/12/13 Orsay

Introduction / 1Introduction / 1stst 4-body 4-body schemescheme

• Two close Förster resonances:→ @ ≈ 79.95V/cm→ @ ≈ 80.4V/cm (quasi-forbidden!)

• A 4-body exchange should be close…

ssp 2423232 2/3

2/52/1 2323242 dps

2/52/3 2323 dp

12Cold Rydberg atoms in LAC04/12/13 Orsay

Results / ResonancesResults / Resonances

• Observe the 2-body resonances:

13Cold Rydberg atoms in LAC04/12/13 Orsay

Results / ResonancesResults / Resonances

• Observe the 4-body resonance:

Observe d state :4-body

energy transfer!

Shift Observed

(79.99V/cm)

14Cold Rydberg atoms in LAC04/12/13 Orsay

Results / Density Results / Density dependancedependance

• Observe p → s → d transfer

No residual linearcross-talk from s

15Cold Rydberg atoms in LAC04/12/13 Orsay

Results / Density Results / Density dependancedependance

• Observe p → s → d transfer

p → d transfergoverned by

4-body process4pd

No residual linearcross-talk from s

16Cold Rydberg atoms in LAC04/12/13 Orsay

Conclusion on Cs Exper.Conclusion on Cs Exper.

• Demonstration of a 4-body interaction→Observed 4-body resonant energy transfer→Studied density dependance→Many-body effect at MOT density for n=23

J. Gurian et al., PRL 108, 023005 (2012)

• Other few-body schemes?→RF to restore resonance?

→Spin mixture?

5 6 7 8 9 10

0,00

0,05

0,10

0,15

0,20

f 5/2m

1/2

f 7/2m

5/2

f 7/2m

3/2

ns+

(n-3

)f7/

2m1/

2

ns+(n+1)s

m5/

2+m

1/2

m3

/2+

m1

/2

m3

/2+

m3

/2

Tra

nsfe

r fr

om 3

2p3/

2m3/

2

Electric field (V/cm)

(n+1)p ns (n+1)s

(n-2

)d5

/2m

1/2+

(n+

1)p 3

/2m

3/2

Too many quasi-forbidden

Resonances in Cs

17Cold Rydberg atoms in LAC04/12/13 Orsay

Towards a new experimentOn Ytterbium Rydberg atoms

18Cold Rydberg atoms in LAC04/12/13 Orsay

Ytterbium experimentYtterbium experiment

• Motivation for 2 electron atom:

Coolinglevels

|r>

|e>

|f>

E=-1/2n2Rydberg

levels

e-

Rydberg electronno longer available

for optical manipulation

e-

e- Second electronis available for

cooling/trapping/imaging

19Cold Rydberg atoms in LAC04/12/13 Orsay

Yb experiment planningYb experiment planning

• Yb cooling and trapping

Zeeman Slower399nm

3D MOT556nm

Yb6s6p 1P1

6s2 1S0

5d6s 3D2

5d6s 3D1

6s6p 3P2

6s6p 3P1

6s6p 3P0

398.8 nm

555.6 nm

t = 5.5 ns

t = 875 ns

Efficient but“hot” limit

Weak but“cold” limit

20Cold Rydberg atoms in LAC04/12/13 Orsay

Yb experiment planningYb experiment planning

• Trapping practical issue: – MOT capture velocity vc8m/s

– Large divergence of Zeeman slower… 2D MOT!

21Cold Rydberg atoms in LAC04/12/13 Orsay

Yb experiment planningYb experiment planning

• Slowing and trapping simulation:– Longitudinal speed Vs position

Position from Zeeman slower start (m)

Longit

udin

al sp

eed (

m/s

)

22Cold Rydberg atoms in LAC04/12/13 Orsay

Yb experiment planningYb experiment planning

• Slowing and trapping simulation:– Longitudinal speed Vs position

Position from Zeeman slower start (m)

Longit

udin

al sp

eed (

m/s

)

23Cold Rydberg atoms in LAC04/12/13 Orsay

Yb experiment planningYb experiment planning

• Slowing and trapping simulation:– Transverse position Vs longitudinal

position

Position from Zeeman slower start (m)

transv

ers

e p

osi

tion (

m)

24Cold Rydberg atoms in LAC04/12/13 Orsay

Yb experiment planningYb experiment planning

• Electrodes and imaging

8 electrodesforming 2 rings

Possibilityto compensate

any field gradient

Holding mechanicsletting all beams pass:16 CF16 + 8 CF40 “in

plane”8 CF16 + 8 CF40 at 45°

2 CF63 at 90°

Under vacuum lens:diffraction limitedimaging of 3µm

25Cold Rydberg atoms in LAC04/12/13 Orsay

Thank you for your attention!

26Cold Rydberg atoms in LAC04/12/13 Orsay

27Cold Rydberg atoms in LAC04/12/13 Orsay

Experimental setupExperimental setup

• Calibrate detection→Direct excitation of each relevant state:

Signal gates

Cross-talk

gatep

s

d

p

s

d

149.4147.3083.0

275.0645.4100.0

082.00645.0016.2

Compute theinversion matrix

to retrieve signal:

(includes ionisation efficiency)

28Cold Rydberg atoms in LAC04/12/13 Orsay

Experimental sequenceExperimental sequence

• Fix electric field• Rydberg excitation + delay • Field ionization pulse + detection• Change electric field and repeat…

29Cold Rydberg atoms in LAC04/12/13 Orsay

Results / ResonancesResults / Resonances

• Minimal toy model:→2 or 4 equidistant atoms at distance R→2 or 4 state basis :

→Compute Rabi oscillation to s or d for each field

• Average over distance R :→2 atoms : Erlang nearest neighbour distribution→4 atoms : Erlang distribution cubed

• Average over field inhomogeneity→ ≈ 5V/cm/cm implies 0.1V/cm over sample

'ss

pp

'pd

ss

'''

''

'

sspd

ssss

sspp

pppp

30Cold Rydberg atoms in LAC04/12/13 Orsay

Ytterbium autoinonisationYtterbium autoinonisation

• Total internal energy > ionisation limit– Autoionisation if nl too small:

• Adiabatic loading of large l states:

e-

e-