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Toward a Stark Decelerator for atoms and molecules exited into a Rydberg state

Toward a Stark Decelerator for atoms and molecules exited into a Rydberg state. Anne Cournol, Nicolas Saquet , Jér ôme Beugnon, Nicolas Vanhaecke, Pierre Pillet. Laboratoire Aime Cotton EGC 2008. 07/03/2008. Cold atoms. Into a gas: cold means weak velocity distribution

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Toward a Stark Decelerator for atoms and molecules exited into a Rydberg state

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  1. Toward a Stark Decelerator for atoms and molecules exited into a Rydberg state Anne Cournol,Nicolas Saquet, Jérôme Beugnon, Nicolas Vanhaecke, Pierre Pillet Laboratoire Aime Cotton EGC 2008 07/03/2008

  2. Cold atoms Into a gas: cold means weak velocity distribution around a mean velocity • Cold? • For what? • How to do? • Precision measurements • Quantum gases • … • Laser cooling • Evaporative cooling • …

  3. Cold molecules? Why ? • High resolution spectroscopy (very long interaction time) • Cold chemistry • Polar molecules : dipole - dipole interaction • Variation of fundamental constants with time (Ye OH) • Parity violation (DeMille BaF,HSiO) • EDM (DeMille PbO, Hinds YbF) Electric Stark decelerator (polar species): Meijer (OH,NH,ND3,CO),Tiemann (SO2), Hinds (YbF,CaF) Optical Stark decelerator: Barker (C6H6) Zeeman decelerator: Merkt (H,D), Raizen (Ne*,O2) Electric Stark decelerator (Rydberg state): Merkt (Ar,H), Softley (H2) How ? • From cold atoms (T<1mK) • Buffer gas cooling (T<1K) • Bolztmann filter (T < 1K) • Rotating nozzle (T~1K) • Beam collision (T~1K) • Deceleration of supersonic molecular beam (T<1K)

  4. Stark deceleration Stark effect: - 2mm 5.5mm SO2: =1.6Debye, 326 stages, L=1.8 m, HV=10kV, =400ns ∆E=0.95cm-1/stage +: Huge density in phase space (conserved by deceleration) -: Dipolar momentum of polar molecules  1Debye

  5. Rydberg state Highly excited electronic state For hydrogen atoms, level energies for Rydberg electron states are: Particle in zero field Particle in electric field Stark effect Dipolar momentum ≈1000 Debye for n=18

  6. Rydberg states into electric field 19d SO2 18d m=2

  7. Stark decelerator for Rydberg states Rydberg states: dipolar momentum ~1000 Debye Lower electric and shapeable field  Constant force Continius deceleration Compact decelerator Versatile decelerator

  8. Outline Supersonic beam Deceleration: simulations 3D Rydberg Excitation

  9. The setup P≈10-8mbar Production of pulsed supersonic beam Experiences

  10. A supersonic beam • Some properties of supersonic beam: • Mean velocity • Axis velocity distribution • Perpendicular velocity distribution Supersonic beam Effusive beam

  11. Sodium pulsed beam Detection by fluorescence induced by laser Rotating sodium target 10 cm 15 cm Detection areas 10 - 50 Hz Ablation laser Nd:YAG@532nm 1.0 mJ/pulse Cw dye laser @589 nm (Tekhnoscan on saturated absorption) Carrying gas~1-10 bar

  12. Time of flight Longitudinal velocity distribution(~10%vexp)

  13. Parameter: ablation energy Carrying gas: Argon Pressure: 6 Bar

  14. Parameter: ablation energy Carrying gas: Argon Pressure: 6 Bar

  15. Parameter: pressure Neon with ablation energy of 0.6 mJ/pulse

  16. Perpendicular temperature Doppler measurement v L

  17. Perpendicular temperature Doppler profile 60 MHz 0 Perpendicular temperature about 1K

  18. Beam characterization • Heating effect when ablating • Beam optimization • Argon (v≈650 m/s) • Axis temperature ≈ 5K • Perpendicular temperature ≈ 1K • Density ≈108atoms/cm3

  19. Excitation toward a Rydberg state Laser excitation

  20. Excitation process Ionisation nd Ti:Sa 920 nm 4P Doubledpulsed dye 330 nm (18d m=2) 3S

  21. 3S-4P First spectrum last week 330 nm Ionisation 4P Doubledpulsed dye 330 nm 3S

  22. 3S-4P 330 nm Ionisation 4P 330 nm 3S 170GHz

  23. Simulations Deceleration: simulations 3D

  24. Particle test: Na • Initial velocity: 370 m/s • Final velocity: 0 m/s • Initial state: 18d • Field : 800 V/cm • Number of electrodes: 20 pairs +V Beam axe -V 1mm 3mm Laser excitation

  25. Experienced force Time for deceleration ~10µs

  26. Distribution of positions Initial cloud: 500000 atomes ∆x=2mm∆v///v//=10%, ∆v/v//=3% No deceleration90% Deceleration10%

  27. Conclusion • Supersonic beam is characterized • Excitation toward a Rydberg state is in process • Simulations show we can stop a cloud of sodium atoms flying initially at 370m/s in 3mm

  28. HV: ±10kV L=1.8m 326 stages Efficiency: 1% Detection by fluorescence HV: ±40V L=3mm 20 ‘stages‘ Efficiency: 10% Ionic detection Conclusion Stark decelerator for atoms and molecules excited into a Rydberg states Stark decelerator (SO2) • One laser to detect the molecules • 4 lasers

  29. Outlook Short time: • Autumn: Rydberg excitation • End of year: Proof of deceleration with 4 electrodes • Spring: Na at standstill Long time: Production of cold Na2, NaH, O, H2O, …

  30. Merci

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