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John T. Costello National Centre for Plasma Science & Technology (NCPST)/ School of Physical Sciences, Dublin City U

Two Colour and Two Photon Ionization Processes in Intense EUV and Optical Fields at F LAS H. John T. Costello National Centre for Plasma Science & Technology (NCPST)/ School of Physical Sciences, Dublin City University www.physics.dcu.ie/~jtc.

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John T. Costello National Centre for Plasma Science & Technology (NCPST)/ School of Physical Sciences, Dublin City U

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  1. Two Colour and Two Photon Ionization Processes in Intense EUV and Optical Fields at FLASH John T. Costello National Centre for Plasma Science & Technology (NCPST)/ School of Physical Sciences, Dublin City University www.physics.dcu.ie/~jtc ' FLASH' - Free Electron LASer in Hamburg Ultrafast Imaging Workshop, Ischia May 3, 2009

  2. Acknowledgements LIXAM (Orsay): D. Cubaynes, M. Meyer Universite Paris 06 (PMC): R. Taieb, A. Maquet DESY (Hamburg): A. Azima, S. Düsterer, P. Radcliffe, H. Redlin, W-B Li, J. Feldhaus PTB (Berlin): A. A. Sorokin, M. Richter Moscow State University: A. N. Grum-Grzhimailo, E. V. Gryzlova, S. I. Strakhova Queen’s University Belfast: Hugo van der Hart Dublin City University: J. Dardis, P. Hayden, P. Hough, T. Kelly, V. Richardson, E. T. Kennedy, J. T. Costello Thanks to AG Photon (R Treusch et al.) & AG Machine (M Yurkov et al.) Ultrafast Imaging Workshop, Ischia May 3, 2009

  3. Collaboration - Origin Collaboration grew out of EU RTD Project: HRPI-CT-1999-50009 Title: “X-Ray FEL Pump Probe Facility” Partners: Orsay, DCU, Lund, MBI, BESSY & DESY Ultrafast Imaging Workshop, Ischia May 3, 2009

  4. Outline of the Talk • FLASH (Brief) Overview • Atoms & Molecules in Intense EUV + NIR Fields Coherent Photoionization Processes in Superposed Fields Optically probing fragments in EUV dissociated H2 • Two Photon Ionization in Intense EUV Fields • Next steps Ultrafast Imaging Workshop, Ischia May 3, 2009

  5. Part 1 - FLASH Overview Ultrafast Imaging Workshop, Ischia May 3, 2009

  6. FLASH Overview RF-gun Diagnostics Accelerating Structures Collimator Undulators Bunch Compressor Bunch Compressor Laser FEL Diagnostics 5 MeV 127 MeV 450 MeV 1000 MeV Bypass • Energy range: ~ 0.3 – 1 GeV •  ~ 6.5 – 60 nm 300 m Ultrafast Imaging Workshop, Ischia May 3, 2009

  7. FLASH: Key Performance Indicators water window Wavelength range (fundamental): 6 - 60 nm FEL harmonics (@13.7 nm): 3 rd : 4.6 nm (270 eV) 5 rd : 2.7 nm (450 eV) Spectral width (FWHM): 0.5-1 % Pulse energy: up to 70 µJ (average), 170 µJ (peak) Pulse duration (FWHM): 10-50 fs Peak power (fundamental): Few GW Average power (fundamental): 0.1 W (up to 3000 pulses / sec) Photons per pulse: ~ 1013 Ackermann et al., Nature Photonics 1 336 (2007)

  8. O/P Profile and Spectral Distribution FEL output builds up from spontaneous emission (photon noise) => SASE – ‘Self Amplified Spontaneous Emission’ Spectral Fluctuations Temporal Fluctuations Ultrafast Imaging Workshop, Ischia May 3, 2009

  9. O/P Profile and Spectral Distribution FEL output builds up from spontaneous emission (photon noise) => SASE – ‘Self Amplified Spontaneous Emission’ Corrected EUV Spectrum Raw EUV Spectrum Ultrafast Imaging Workshop, Ischia May 3, 2009

  10. Part 2 - Experiments on dilute targets with FLASH Motivations 1. ‘FLASH’ Characterisation 2. Demonstration Experiments 3. Future (Pathfinding) Ultrafast Imaging Workshop, Ischia May 3, 2009

  11. Atoms & Molecules in Intense EUV + Optical (800/400 nm) fields Photoionization of rare gas atoms dressed by intense optical fields 2. Optical probing EUV dissociated H2 Summary of AMOP@FLASH http://hasylab.desy.de/science/user_collaborations/amopflash Photoionization Experiments with the Ultrafast EUV Laser FLASH - Free Electron Laser in Hamburg J T Costello, J Phys Conf Ser 88 Art No 012057 (2007) C. Bostedt et al., Experiments at FLASH, Nucl. Inst. Meth. in Res. A 601 108-122 (2009) Ultrafast Imaging Workshop, Ischia May 3, 2009

  12. FLASH NIR/Vis and EUV Beam Layout PG2 BL1 BL2 visible laser light BL3 Ultrafast Imaging Workshop, Ischia May 3, 2009

  13. Two colour ATI/ Laser Assisted PES hwir =1.55eV Sideband intensity very Sensitive to overlap Superposition of visible and VUV pulses in a noble gas jet Schins et al. PRL 73, 2180 (1994) Electron Spectrometer VUV Visible fs laser pulse 15.76 eV Ar(IP) gas jet E.S. Toma et al. PRA 62 061801 (2000)

  14. Two colour ATI/ Laser Assisted PES Experimental Layout at FLASH - (EU-RTD) P. Radcliffe, et al., Nucl. Instr. and Meth. A 83, 516-525 (2007)

  15. Two colour ATI/ Laser Assisted PES Sideband number/intensity depend strongly on EUV/NIR overlap  by comparison with theory we are able to determine relative time delay to better than 100 fs 550 fs 1. New ultrafast EUV-modulated optical-reflectivity methods 2. ‘TEO’ C. Gahl et al., Nature Photonics 2 165-169 (2008) A. Azima et al., APL. T. Maltezopoulos et al., New J Phys 10 Art. No. 033026 (2008) (In Press 2009) P. Radcliffe, et al., Nucl. Instr. and Meth. A 83, 516-525 (2007) P Radcliffe, et al., APL 90 131108 (2007)

  16. Two colour ATI - ‘Soft Photon’ One photon cross-section ‘n’ photon ATI cross-section - Classical excursion vector of an electron in a laser field of amplitude - Momentum transfer After a little work………….sideband strength is given by an expression like…… Jn - Bessel function (first kind order ‘n’) kn - Shifted wavenumber of the ejected electron = - Usual asymmetry parameter A Maquet and R Taieb, J. Mod. Opt. 54 1847 (2007)

  17. Two colour ATI - Z Scaling 800 nm Ti-Sa 1.55 eV/ 120 fs FLASH h ~ 93 eV 20 J/pulse

  18. Two colour ATI - Z Scaling Intesnity ratio of n= 1:2 sidebands - Model vs Experiment Fitted 800 nm intensity ~ 5 x 1011 W.cm-2 Experiment ‘Soft Photon’ Ultrafast Imaging Workshop, Ischia May 3, 2009

  19. 2 colour ATI - FEL Wavelength Scaling FEL + 800 nm. SB Ratio - Comparison of SPA with Experiment Ultrafast Imaging Workshop, Ischia May 3, 2009

  20. 2 colour ATI - Optical Intensity Scaling Ne: Asymmetry in sideband distribution Ultrafast Imaging Workshop, Ischia May 3, 2009

  21. 2 colour ATI - Optical Intensity Scaling Ne: ‘Toy’ SFA Code / Asymmetry in sideband distribution Ne: Simulation hFEL = 46 eV Ultrafast Imaging Workshop, Ischia May 3, 2009 Ultrafast Imaging Workshop, Ischia May 3, 2009

  22. Atomic Dichroism in Two colour ATI Strong Polarisation Dependence of Sidebands (Low Field) He 1s2 + hXUV ----> He+ 1s + p He 1s2 + hXUV+ hOL ---> He+ 1s + s, d FLASH: 13.7 nm, 10-20 fs, 20µJ OL: 800nm, 4ps, 400µJ, 6 x 1011 W/cm2  Meyer et al., PRL 101 Art. no. 193002 (2008)

  23. Atomic Dichroism in Two colour ATI - He Low Optical Laser Field High Optical Laser Field () = 3Sd + (5Ss + Sd) cos2 Ss/Sd =1.25 ± 0.3 P. Theory: A Grum-Grzhimailo et al. SPA: A Maquet/ R Taieb Meyer et al., PRL 101 Art. no. 193002 (2008)

  24. Atomic Dichroism in Two colour ATI - Kr AD in TC-ATI: Ne, Kr, Xe: work in progress FLASH: 13.7 nm, 10-20 fs, 20µJ OL: 800nm, 4ps, 6 x 1011 W/cm2 Ultrafast Imaging Workshop, Ischia May 3, 2009

  25. Atomic Dichroism in 2 colour ATI - Ne+ Sequential Ionization ‘Work in progress’ - but we can begin to think about studying isonuclear trends……. Ultrafast Imaging Workshop, Ischia May 3, 2009

  26. Summary - Two Colour ATI Demonstrated interference free SBs to high order, polarisation control, laser and FEL parameter dependencies & SBs in atomic and ionic targets At low optical intensities 2nd OPT & SPA agree 3. Beyond He we really need to measure angular distributions to try to unravel the ‘l’ channels… 4. SPA works well at high intensities but the number of open high angular momentum channels is a challenge for other approaches such as R-Matrix Floquet (HvdH) 5. Is there really value in going beyond SPA here ? Does the residual ion core atomic structure really matter….? Ultrafast Imaging Workshop, Ischia May 3, 2009

  27. Optical Probing of H2 Dissociation Demonstration Experiment Ultrafast Imaging Workshop, Ischia May 3, 2009

  28. Optical Probing of H2 Dissociation 1) H2 + h(FEL) --> H + H* < 100 fs FEL : 13.7 nm, 90.5 eV 2) H* + h(las) --> H+ + e- hVUV Opt.Las. : 400 nm, 3.1 eV H+ + H+ H+ + H(nl) H+ + H(1s) H(1s) + H(1s) Ultrafast Imaging Workshop, Ischia May 3, 2009

  29. Optical Probing of H2 Dissociation 13.7 nm (pump) + 400 nm (probe) High Intensity (1.5 mJ/120 fs) Low Intensity (0.5 mJ/120 fs) Ultrafast Imaging Workshop, Ischia May 3, 2009

  30. Optical Probing of H2 Dissociation Dynamics - more to do - jitter limited. expt. fit risetime = 500 fs Ultrafast Imaging Workshop, Ischia May 3, 2009

  31. Xe ionization in intense EUV fields Ultrafast Imaging Workshop, Ischia May 3, 2009

  32.  4d two photon direct ionization FEL only. h ~ 93 eV Xe + 2h Xe+ + e- Replace PIS by MBES - First evidence of inner-shell TPI Ultrafast Imaging Workshop, Ischia May 3, 2009

  33. Part 3. Current and Future Interests Two Colour Resonant Photoionization Processes To date we have looked only at one and two colour non-resonant processes 2. Next phase - FEL tunable and so we can explore resonanttwo colour processes where inner shell electrons dominate Ultrafast Imaging Workshop, Ischia May 3, 2009

  34. Kr (3d94d) 2 Photon Resonance Auger Expt. June 2009 (Hopefully) MLM - 3 degree incidence Kr+ 3d92D5/2 92.0eV 4d Auger ? Kr+ 4p4 4d, 5d VUV 46.1 eV Kr 3d10 4s2 4p6 Ultrafast Imaging Workshop, Ischia May 3, 2009

  35. Kr (3d94d) DOR-Auger First Effort: Resonant Auger Spectrum 4p 4s FEL+las FEL SB TOF (ns) Kr+ 3d92D5/2 92.0eV 4d Auger 1.55 eV 5p ? Kr+ 4p4 4d, 5d XUV 13.9 nm Kr 3d10 4s2 4p6 Next Expt:hFEL (89 eV) + hOL(3.1 eV) Ultrafast Imaging Workshop, Ischia May 3, 2009

  36. Experiments post-upgrade Upgrade - Optical Parametric Amplifier - (fs OPA) Laser coupling/spectroscopy of autoionization states - 'Autler-Townes' meets ‘Codling-Madden’ Ultrafast Imaging Workshop, Ischia May 3, 2009

  37. Tunable Optical Laser - Laser Coupling of autoionization states - 'Autler Townes' Autoionizing Resonances - He Laser Coupled Autoionising State Dynamics ‘New Knobs’ Laser Frequency Laser Intensity Bachau & Lambropoulos, PRA (1986) Themelis, Lambropoulos, Meyer, JPB (2005) Ultrafast Imaging Workshop, Ischia May 3, 2009

  38. FLASH - Technical Developments OPA Upgrade - 0.01 - 1 mJ/ 0.1 - 20 ps Synchronisation -New FIR Undulator (THz) Seeding with HHs - Full coherence Stabilisation Synchroniosation Ultrafast Imaging Workshop, Ischia May 3, 2009

  39. In Conclusion 1. To date we have looked only at one and two colour non-resonant photoionization processes Now - FEL easily tunable - we can explore resonanttwo colour processes where inner shell electrons dominate 3. Study fragmentation and ionization from vibrationally excited/selected wavepackets in simple molecules Beyond 2009: Seeding, fs jitter, angle resolved PES,… LCLS/XFEL/SPRING-8/NLS……….. Ultrafast Imaging Workshop, Ischia May 3, 2009

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