1. Sharly Fleischer, Yan Zhou, Robert W. Field, Keith A. Nelson FRISNO 11 Orientation and Alignment of Gas Phase Molecules by Single Cycle THz Pulses

2. Multiphoton Ionization Self focusing & Filamentation High Harmonic Generation Ultrafast x-ray diffraction Up – Down Symmetry Conserved

3. DC field + - Not Field Free !

4. Sakai and colleagues: DC electric field + laser pulse with adiabatic turn-on and nonadiabatic turn-off. Approaches for field – free orientation A. Goban, S. Minemoto, and H. Sakai, “Laser-Field-Free Molecular Orientation,“ Phys. Rev. Lett. 101, 013001 (2008).

5. Vrakking and colleagues: Hexapole state selector (Producing molecules in a single quantum state) + a combination of a DC and intense fs laser field. Approaches for field – free orientation O. Ghafur, A. Rouzée, A. Gijsbertsen, W. K. Siu, S. Stolte and M. J. J. Vrakking, “Impulsive orientation and alignment of quantum-state-selected NO molecules,” Nature Phys. 5, 289-293 (2009).

6. Approaches for field – free orientation L. Holmegaard, J. L. Hansen, L. Kalhøj, S. L. Kragh, H. Stapelfeldt, F. Filsinger, J. Küpper, G. Meijer, D. Dimitrovski, M. Abu-samha, C. P. J. Martiny and L. B. Madsen, “Photoelectron angular distributions from strong- field ionization of oriented molecules,” Nature Phys. 6, 428-432 (2010). Holmegaard and colleagues: Electrostatic quantum state selector + deflector combination of a DC and femstosecond laser field.

7. Kling and colleagues: Approaches for field – free orientation two-color excitation scheme in which the fundamental laser frequency (800 nm) is mixed with its second harmonic with a specified relative phase. S. De, I. Znakovskaya, D. Ray, F. Anis, Nora G. Johnson, I. A. Bocharova, M. Magrakvelidze, B. D. Esry, C. L. Cocke, I.V. Litvinyuk, and M. F. Kling “Field-Free Orientation of CO Molecules by Femtosecond Two-Color Laser Fields,” Phys. Rev. Lett. 103, 153002 (2009).

8. Optical Pulse vs. Half Cycle Pulse 1.3 fs

9. Ultrashort optical pulse Half cycle pulse AlignmentOrientation

10. Population Transfer Coherences Alignment Density matrix – non resonant

11. Population Transfer Coherences Alignment x x x x x x x x x x x x x Density matrix – non resonant

12. Population Transfer Coherences Orientation Density matrix - resonant

13. Population Transfer Coherences Orientation and Alignment Density matrix - resonant

14. ResonantNon resonant May induce all the rotational cohernces May induce only even rotational coherences No orientation Only alignment Both orientation and alignment Short summary

15. Intense single cycle THz pulse K. L. Yeh, M. C. Hoffmann, J. Hebling and K. A. Nelson, “Generation of 10 μJ ultrashort THz pulses by optical rectification”, Appl. Phys. Lett. 90, 171121 (2007); LiNb

16. “But you don’t have a Half Cycle Pulse !!!” Time (ps) Amplitude (a.u)

17. Time (ps) Amplitude (a.u) Frequency (THz) Spectral Amplitude (noramlized) ResonantNon - Resonant Time(ps) J states (m=0) Amplitude (a.u) Population Transfer J,J+1 coherences J,J+2 coherences

19. Revival

20. Quantum revivals of rotational wave packets Rotational energy: Rotational wave packet: Quantum revival time: The wavefunction is periodic: - full revival 02 6 12 2030 Accumulated phase

21. O=C=S BS G LiNb Laser Pellicle BS ZnTeW PD Delay EO sampling

22. 1 T rev 2 T rev 3 T rev Time (ps) Amplitude (a.u) EO sampling, OCS, 250torr Reflections

23. O=C=S BS G LiNb Laser Delay PPD Pellicle BS BS P 45 0 to THz polarization Pellicle BS ZnTeW PD Delay Detection of Molecular Alignment

24. Time (ps) Intensity (a.u.) Population Transferred To higher J’s Alignment of OCS, 350torr, 300K

25. Each molecule is forced to rotate in a plane Non thermal rotational distribution Time independent alignment

26. Time (ps) Intensity (a.u.) Decay of population (T 1 )

27. Decay of coherence (T 2 ) Time (ps) Intensity (a.u.)

28. Rotational state distribution (J) Intensity (a.u.)

29. Experimental alignment factor

31. Max Orientation @ 1T rev (x10 2 ) Max Alignment @ 1/2T rev (x10 4 ) Peak field amplitude (a.u.) Max Alignment=1.207x10 -4 x Peak 2 Max Orientation=1.441x10 -2 x Peak Time (ps) Amplitude (a.u) 1% orientation 5% orientation8% orientation

32. Summary Table top single cycle THz pulses can induce significant field-free orientation under ambient conditions Relatively high orientation is not necessarily associated Requires with high degree of alignment. With jet cold molecular samples, higher degree of orientation is expected. Combining optical and THz pulses may enable two independent handles for manipulating molecular angular distributions in 3D.

33. Thank you