Sharly Fleischer , Yan Zhou, Robert W. Field, Keith A. Nelson

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

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

3. + - DC field Not Field Free !

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

5. Approaches for field – free orientation Vrakking and colleagues: Hexapole state selector (Producing molecules in a single quantum state) + a combination of a DC and intense fs laser field. 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,” NaturePhys. 5, 289-293 (2009).

6. Approaches for field – free orientation Holmegaard and colleagues: Electrostatic quantum state selector + deflector combination of a DC and femstosecond laser field. 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).

7. Approaches for field – free orientation Kling and colleagues: 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 Alignment Orientation

10. Density matrix – non resonant Population Transfer Coherences Alignment

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

12. Density matrix - resonant Population Transfer Coherences Orientation

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

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

15. Intense single cycle THz pulse LiNb 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);

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

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

19. Revival Revival

20. EO sampling PD ZnTe W PD Pellicle BS O=C=S G LiNb Delay Laser BS

21. EO sampling, OCS, 250torr 1 Trev 2 Trev 3 Trev Amplitude (a.u) Reflections Reflections Time (ps)

22. Detection of Molecular Alignment PD ZnTe W PD Pellicle BS Pellicle BS O=C=S P PD 450 to THz polarization P G LiNb Delay Delay Laser BS BS

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

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

25. Decay of population (T1) Intensity (a.u.) Time (ps)

26. Decay of coherence (T2) Intensity (a.u.) Time (ps)

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

28. Experimental alignment factor

30. Amplitude (a.u) 8% orientation 5% orientation 1% orientation Time (ps) Max Orientation=1.441x10-2 x Peak Max Orientation @ 1Trev (x102) Max Alignment @ 1/2Trev(x104) Max Alignment=1.207x10-4 x Peak2 Peak field amplitude (a.u.)

31. 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.

32. Thank you