1. Marina Quintero-Pérez Paul Jansen Thomas E. Wall Wim Ubachs Hendrick L. Bethlem

2. Motivation Why cold molecules? Long coherence times High precision measurements COLD = low velocities

3. Need: Molecules travelling at 3 m/s Sensitive to variation of the proton-to-electron mass ratio Motivation Why a molecular fountain? Measure the inversion frequency of ammonia v = 3 m/s L= 30 cm ∆t = 0.5 sec ∆f = 1 Hz

4. ion detector Experimental set-up Poor efficiency at low velocities PROBLEM: - Couplings - Overfocusing Stark decelerator v~300 m/s v~100 m/s

5. 336 rings separated by 1.5 mm Voltage applied by 8 HV amplifiers -5 ≤ V ≤ 5 kV 0 ≤ f ≤ 15 kHz (v max ~150 m/s) SOLUTION: RING DECELERATOR Experimental set-up v~300 m/s v~100 m/s

6. Fixed time Ring decelerator: operating principle Variation with time V n = V 0 sin(-2πft+2πn/8)

7. Inversion splitting much smaller in ND 3 than NH 3 ND 3 Stark shift - greater - very linear Comparing NH 3 and ND 3 STARK SHIFT

8. NH 3 Guiding ND 3

9. NH 3 ND 3 Guiding Decelerating

10. NH 3 ND 3 Quintero-Pérez et al., PRL 110, 133003 (2013) Guiding Decelerating Trapping

11. Guiding Decelerating Trapping for 50 ms ND 3 Quintero-Pérez et al., PRL 110, 133003 (2013) NH 3

12. Reducing the trap depth ND 3 t ramp = 2 ms t ramp = 10 µs t ramp

13. Modulating the trap ND 3 NH 3

14.  First trapping on a ring decelerator (avoiding losses at low velocity)  Great control over the trapped molecules - Measurement of the characteristic frequencies - Cooling - Phase space manipulation Conclusions and Outlook High enough density of molecules at 3 m/s? A Molecular Fountain!

15. Questions?

16. Trap position Inside a ring Between two rings

17. Trap position

18. Transverse oscillations

19. Oscillations

20. ND 3 and NH 3 14 mK 100 mK

21. Effect of T ramp on signal A measure of adiabaticity 5 kV – 2 kV – 5 kV

22. Electric field Inside a ring Between two rings

23. Phase* jumps vzvz a z = 0a z < 0a z > 0 * Phase = Position of trap centre

24. Phase jumps |a| = 15,000 m/s 2 ; T trap = 50 ms 90 – 0 – 90 m/s 70 – 0 – 70 m/s