1. A Stark decelerator for ammonia molecules
Ruth Buning
Master research project
LCVU Amsterdam
Supervisor: Rick Bethlem

2. Motivation High resolution spectroscopy Collisions
Variation of constants of nature
Collisions

3. Motivation High resolution spectroscopy Ammonia, NH3
Proton-electron mass ratio m=me/mp

4. Motivation Variation of m=me/mp
On a cosmological timescale:
Compare H2 spectra of different epochs:
Lab
today
QSO
12 Gyr ago

5. Reinhold et al, PRL 96 (2006)
Ubachs et al, JMS 241 (2007) 155

6. Motivation Variation of m=me/mp
In the lab:
Compare ‘clocks’
Sensitivity to me/mp
Comparison time
Accuracy
Ammonia
NH3
Ceasium Cs

7. High resolution spectroscopy
Transit-time broadening

8. Even higher resolution..
Fountain, clock

9. How can we produce and detect as much slow NH3 as possible?
The Stark decelerator
How can we produce and detect as much slow NH3 as possible?

10. Dipole in E field
Stark shift:

11. Stark shift in ammonia
Low-field seekers
High-field seekers

12. Dipole in E field (2)

13. Deceleration
Also: transverse focusing

14. Setup

16. Molecular beam Pulsed beam Supersonic expansion Few % NH3 in Xe
Valve cooling

17. The decelerator

18. Time to switch

19. Time to switch

20. Detection
2+1 REMPI
Resonance
Enhanced
Multi
Photon
Ionization

21. Measurements
Wavelength scan
TOF (time of flight) scan

22. Spectrum
Low field seeking state
Decelerator off
Decelerator at 3 kV

23. TOF profile

24. TOF profile

25. TOF profile

26. Optimization Beam quality Detection efficiency Ammonia percentage
Temperature valve
Stagnation pressure
Detection efficiency
Laser power and focus

27. Optimization Beam quality Detection efficiency Ammonia percentage 5 %
Temperature valve -50 oC
Stagnation pressure 0.5 bar
Detection efficiency
Laser power and focus ~15 mJ/p

28. Slow ammonia (1)
100 m/s

29. Slow ammonia (2)

30. Conclusions Stark decelerator operational Down to 25 m/s Adaptations
Differential pumping
Focusing
-> Molecular fountain

31. Fountain

38. Outline Why decelerate? Why ammonia?
Neutral polar molecules in E fields
The machine
Slow ammonia

39. Optimization Beam quality Detection efficiency Ammonia percentage 5 %
Temperature
Backing pressure
Valve opening
Detection efficiency
Laser power
Laser focus

40. Optimization Beam quality Detection efficiency Ammonia percentage 5 %
Temperature oC
Backing pressure
Valve opening
Detection efficiency
Laser power
Laser focus

41. Optimization Beam quality Detection efficiency Ammonia percentage 5 %
Temperature oC
Backing pressure
Valve opening
Detection efficiency
Laser power
Laser focus

42. Backing pressure

43. Clusters

44. Optimization Beam quality Detection efficiency Ammonia percentage 5 %
Temperature oC
Backing pressure 0.5 bar
Valve opening
Detection efficiency
Laser power
Laser focus

45. Valve opening

46. Optimization Beam quality Detection efficiency Ammonia percentage 5 %
Temperature oC
Backing pressure 0.5 bar
Valve opening
Detection efficiency
Laser power
Laser focus

47. Laser power

48. Slow ammonia (2)

49. Slow ammonia (2)

50. Slow ammonia (2)

51. Slow ammonia (3)

52. Slow ammonia (3)

53. Slow ammonia (3)

54. Slow ammonia (3)