1. Alternate Gradient deceleration of large molecules
Kirstin Wohlfart, Frank Filsinger, Fabian Grätz,
Gerard Meijer and Jochen Küpper
Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany
International Symposium on Molecular Spectroscopy, Columbus 2007

2. Motivation Towards trapping of large molecules.
Large / heavy molecules have practically only high-field seeking states.  Study of intrinsic properties of biomolecules.  Fundamental physics: • Energy difference of enantiomers • Electric dipole moment of electron.
Ground state of any molecule is high-field seeking.
Alternate Gradient (AG) deceleration: Deleceleration of polar molecules in both low-field seeking and high-field seeking states.

3. Stark effect

4. Stark effect

5. Longitudinal motion

6. Alternate Gradient principle
E(y): focusing for lfs and defocusing for hfs. E(x): defocusing for lfs and focusing for hfs.

7. Alternate Gradient principle
E(y): focusing for lfs and defocusing for hfs. E(x): defocusing for lfs and focusing for hfs.

8. Experimental setup
Pulsed supersonic jet of benzonitrile in Xe (  310 m/s) or HNO3 in Xe, production of OH by photodissociation (  350 m/s).
27 dipole lenses: each 13 mm long, diameter 6 mm; total length 54 cm, applied voltages: ±15 kV (140 kV/cm).
Excitation with cw UV, P ≥ 5 mW,  = 1 MHz.
Detection of integrated LIF using time-resolved photon counting.

9. Experimental setup

10. Focusing and deceleration of lfs OH

11. Focusing and deceleration of lfs OH

12. Focusing and deceleration of lfs OH

13. Focusing and deceleration of lfs OH
> 50 % of kinetic energy removed!

14. Phase space distribution: Deceleration from 345 m/s to 276 m/s

15. Phase space distribution: Deceleration from 345 m/s to 276 m/s

16. Focusing and deceleration of hfs OH

17. Focusing and deceleration of hfs OH

18. Focusing and deceleration of hfs OH

19. Focusing and deceleration of hfs OH
> 20 % of kinetic energy removed!

20. S1  S0 spectrum of benzonitrile
J´Ka´Kc´ J´´Ka´´Kc´´
FWHMLorentz = 8 MHz
FWHMGauß = (3.4 ± 0.5) MHz
FWHMVoigt = (9.3 ± 0.3) MHz

21. Focusing and deceleration of benzonitrile

22. Focusing and deceleration of benzonitrile
> 20 % of kinetic energy removed!

23. Conclusions and outlook
Deceleration of OH in low-field seeking and high-field seeking states.
Decelerating of polar molecules in both high-field seeking and low-field seeking states in one setup is possible.
Deceleration of benzonitrile.

24. Conclusions and outlook
Deceleration of OH in low-field seeking and high-field seeking states.
Deceleration of polar molecules in both high-field seeking and low-field seeking states in one setup is possible.
Deceleration of benzonitrile.
Extension of apparatus for deceleration of OH and benzonitrile to a standstill.

25. Conclusions and outlook
Deceleration of OH in low-field seeking and high-field seeking states.
Decelerating of polar molecules in both high-field seeking and low-field seeking states in one setup is possible.
Deceleration of benzonitrile.
Extension of apparatus for deceleration of OH and benzonitrile to a standstill.
Deceleration of larger molecules: tryptophan, etc.

26. Acknowledgement Molecular physics department of Fritz-Haber-Institut
DFG Schwerpunktprogramm 1116
Max-Planck-Gesellschaft

27. Focusing properties
Deceleration lfs OH from 345 m/s to 303 m/s, bunching length d = 6 mm.

28. Bunching properties
Deceleration lfs OH from 345 m/s to 303 m/s, focusing length f = 3 mm

29. Misalignment

30. Focusing of benzonitrile
000
606

31. First lfs OH focusing measurements
± 5 kV
experiment
simulation

32. Focusing and deceleration of CO

33. Motivation
Getting complete control over both the internal and external degrees of freedom of molecules.
beams of molecules in a single (subset of) quantum state(s).
spatially oriented molecules.
beams of molecules with a computer controlled velocity distribution.
Slow molecular beams for metrology; sensitive symmetry tests.
weak interactions in chiral molecules.
time-reversal violating electric dipole moment of the electron (EDM).
Novel molecular beam collision, reaction, and interferometry experiments.
collisions at variable, well-defined, energies; scattering resonances.
Producing samples of trapped (cold) molecules; degenerate molecular gases.
anisotropic dipole-dipole interaction repulsive attractive
Study of intrinsic properties of biomolecules.

34. How to produce Cold Molecules
(Photo)-association of cold atoms:
alkali dimers:
translationally cold, typically vibrationally highly excited.
Feshbach resonances:
molecular BECs.
heteronuclear (polar!) alkali dimers.
Buffergas cooling:
general cooling method; electronic and vibrational ground state.
Starting with a molecular beam.
Retracting beam-source; back-spinning nozzles.
Extracting beams from a cryogenic container.
Filtering of slow molecules from an effusive beam.
Billiard-like collisions in crossed molecular beams.
Deceleration of molecular beams with optical fields.