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-