P. Cheinet, B. Pelle, R. Faoro, A. Zuliani and P. Pillet Laboratoire Aimé Cotton, Orsay (France) Cold Rydberg atoms in Laboratoire Aimé Cotton 04/12/2013

2 Cold Rydberg atoms in LAC04/12/13Orsay Outline Introduction: –Rydberg atoms and their properties Cold cesium experiment A new experiment on Ytterbium

3 Cold Rydberg atoms in LAC04/12/13Orsay Introduction: Rydberg atom Rydberg atom = highly excited atom e-e- Cooling levels |r> |e> |f> E=-1/2n 2 Rydberg levels Failed screening at the core imply quantum defects Most weight at large r!

4 Cold Rydberg atoms in LAC04/12/13Orsay Introduction: Rydberg atom Zimmerman et al Ionization

5 Cold Rydberg atoms in LAC04/12/13Orsay Introduction: Rydberg atom 23p 3/2 23s 24s Resonant energy ≈ 80V/cm

6 Cold Rydberg atoms in LAC04/12/13Orsay Introduction: 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

7 Cold Rydberg atoms in LAC04/12/13Orsay Cs experiment

8 Cold Rydberg atoms in LAC04/12/13Orsay Experimental setup Sequence=MOT,Rydberg,delay,ionisation Ions extracted through the 2 holes to the MCP Up to 5kV ramp applied between the 2 central grids MCP Delay = 1.5 μ s (frozen!) Then TOF recorded on MCP

9 Cold Rydberg atoms in LAC04/12/13Orsay Cs exper./ 4-body interaction Two close Förster resonances: ≈ 79.95V/cm ≈ 80.4V/cm (quasi-forbidden!) A 4-body exchange should be close… 23p 3/2 23s 24s 23p 1/2 23d 5/2 TOF! d state is a signature of 4-body energy transfer!

10 Cold Rydberg atoms in LAC04/12/13Orsay Cs exper./ 4-body interaction Two close Förster resonances: ≈ 79.95V/cm ≈ 80.4V/cm (quasi-forbidden!) A 4-body exchange should be close…

11 Cold Rydberg atoms in LAC04/12/13Orsay Introduction / 1 st 4-body scheme Two close Förster resonances: ≈ 79.95V/cm ≈ 80.4V/cm (quasi-forbidden!) A 4-body exchange should be close…

12 Cold Rydberg atoms in LAC04/12/13Orsay Results / Resonances Observe the 2-body resonances:

13 Cold Rydberg atoms in LAC04/12/13Orsay Results / Resonances Observe the 4-body resonance: Observe d state : 4-body energy transfer! Shift Observed (79.99V/cm)

14 Cold Rydberg atoms in LAC04/12/13Orsay Results / Density dependance Observe p → s → d transfer No residual linear cross-talk from s

15 Cold Rydberg atoms in LAC04/12/13Orsay Results / Density dependance Observe p → s → d transfer p → d transfer governed by 4-body process No residual linear cross-talk from s

16 Cold Rydberg atoms in LAC04/12/13Orsay 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, (2012) Other few-body schemes? → RF to restore resonance? → Spin mixture? Too many quasi-forbidden Resonances in Cs

17 Cold Rydberg atoms in LAC04/12/13Orsay Towards a new experiment On Ytterbium Rydberg atoms

18 Cold Rydberg atoms in LAC04/12/13Orsay Ytterbium experiment Motivation for 2 electron atom: Cooling levels |r> |e> |f> E=-1/2n 2 Rydberg levels e-e- Rydberg electron no longer available for optical manipulation e-e- e-e- Second electron is available for cooling/trapping/imaging

19 Cold Rydberg atoms in LAC04/12/13Orsay Yb experiment planning Yb cooling and trapping Zeeman Slower 399nm 3D MOT 556nm Yb 6s6p 1 P 1 6s 2 1 S 0 5d6s 3 D 2 5d6s 3 D 1 6s6p 3 P 2 6s6p 3 P 1 6s6p 3 P nm nm t = 5.5 ns t = 875 ns Efficient but “hot” limit Weak but “cold” limit

20 Cold Rydberg atoms in LAC04/12/13Orsay Yb experiment planning Trapping practical issue: –MOT capture velocity v c  8m/s –Large divergence of Zeeman slower… 2D MOT!

21 Cold Rydberg atoms in LAC04/12/13Orsay Yb experiment planning Slowing and trapping simulation: –Longitudinal speed Vs position Position from Zeeman slower start (m) Longitudinal speed (m/s)

22 Cold Rydberg atoms in LAC04/12/13Orsay Yb experiment planning Slowing and trapping simulation: –Longitudinal speed Vs position Position from Zeeman slower start (m) Longitudinal speed (m/s)

23 Cold Rydberg atoms in LAC04/12/13Orsay Yb experiment planning Slowing and trapping simulation: –Transverse position Vs longitudinal position Position from Zeeman slower start (m) transverse position (m)

24 Cold Rydberg atoms in LAC04/12/13Orsay Yb experiment planning Electrodes and imaging 8 electrodes forming 2 rings Possibility to compensate any field gradient Holding mechanics letting all beams pass: 16 CF CF40 “in plane” 8 CF CF40 at 45° 2 CF63 at 90° Under vacuum lens: diffraction limited imaging of  3µm

25 Cold Rydberg atoms in LAC04/12/13Orsay Thank you for your attention!

26 Cold Rydberg atoms in LAC04/12/13Orsay

27 Cold Rydberg atoms in LAC04/12/13Orsay Experimental setup Calibrate detection → Direct excitation of each relevant state: Signal gates Cross-talk Compute the inversion matrix to retrieve signal: (includes ionisation efficiency)

28 Cold Rydberg atoms in LAC04/12/13Orsay Experimental sequence Fix electric field Rydberg excitation + delay Field ionization pulse + detection Change electric field and repeat…

29 Cold Rydberg atoms in LAC04/12/13Orsay Results / 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

30 Cold Rydberg atoms in LAC04/12/13Orsay Ytterbium autoinonisation Total internal energy > ionisation limit –Autoionisation if nl too small: Adiabatic loading of large l states: e-e- e-e-