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John T. Costello

Two Colour and Two Photon Ionization Processes in Intense XUV 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

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  1. Two Colour and Two Photon Ionization Processes in Intense XUV 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 UXSS - SLAC. June 18, 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.) UXSS - SLAC. June 18, 2009

  3. DCU Intense Laser Matter Research 6 laboratory areas focussed on pulsed laser matter interactions (NIR – X-ray/ 30fs – 30 ns, spectroscopy/ imaging/PLD) Academic Staff (5): John T. Costello, Eugene T. Kennedy, Jean-Paul Mosnier, Lampros Nikolopoulos and Paul van Kampen Current Postdocs (2): Dr. Patrick Hayden, Dr. Sateesh Krishnamurty (Incoming - Subhash Singh) Current PhD students (13 + 1): John Dardis, Jack Connolly, Brian Doohan, Colm Fallan, Padraig Hough, Eanna Mac Carthy, , Mossy Kelly, Conor McLaughlin, Ricky O'Haire, Vincent Richardson, Dave Smith, Tommy Walsh & Jiang Xi, open position (with LN) Recent PhD Graduates: Caroline Banahan, Mark Stapleton, Jonathan Mullen, Kevin Kavanagh, Eoin O’Leary Recent Postdocs: Deirdre Kilbane, Hugo de Luna, Jofre Gutieriez-Pedrogosa, Brendan Doggett, Subo Chakraborti and Jean-Rene Duclere Funded by: SFI - Frontiers and Investigator HEA – PRTLI (Kit) IRCSET (People) EU - Marie Curie (People) UXSS - SLAC. June 18, 2009

  4. DCU Intense Laser Matter Research 6 laboratory areas focussed on pulsed laser matter interactions (NIR – X-ray/ 30fs – 30 ns, spectroscopy/ imaging/PLD) • Research Domains: • Photoionization of Atoms and Ions with Laser Plasma, Synchrotron and Free Electron Laser Light Sources(JC, PVK, ETK, LN) • Optical Diagnostics of Laser Produced Plasmas (JC) • Laser Induced Breakdown Spectroscopy – LIBS (JC, ETK) • Pulsed Laser Deposition (PLD) of Materials (JPM) • Some Current Projects: • Two colour photoionization of atoms with XUV FELs (& LPLS) • UV-Vis imaging, spectroscopy and interferometry of colliding laser produced plasmas (with Sivandan ‘Hari’ Harilal, Purdue) • Colliding plasma targets for EUVL light sources (with UCD & TCD) • VUV-LIBS for Elemental Characterisation in Steel • PLD and in-situ P-type doping of ZnO nanostructures UXSS - SLAC. June 18, 2009

  5. 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 UXSS - SLAC. June 18, 2009

  6. What are the USPs of XFELs in AMOP ? Few-photon single and multiple ionization processes Ultra-dilute targets Photo-processes with ultralow cross-sections 4. Pump and probe experiments (XUV + XUV or XUV + Opt.) Single shot measurements Brings inner-shell electrons into non-linear processes Re-asserts primacy of the photon over field effects* ! *See USP No. 1 UXSS - SLAC. June 18, 2009

  7. Outline of the Talk • FLASH (Brief) Overview • Atoms in Intense XUV + NIR Fields 1. Coherent Photoionization Processes in Superposed Fields 2. Few Femtosecond X-ray Photoionization Processes at LCLS • Two Photon Ionization in Intense XUV Fields • Next Steps UXSS - SLAC. June 18, 2009

  8. Part 1 - FLASH Overview UXSS - SLAC. June 18, 2009

  9. 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 UXSS - SLAC. June 18, 2009

  10. 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 50 µJ (average), 120 µJ (peak) Pulse duration (FWHM): 10-30 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)

  11. O/P Profile and Spectral Distribution FEL output builds up from spontaneous emission (photon noise) => SASE – ‘Self Amplified Spontaneous Emission’ Spectral Fluctuations Temporal Fluctuations UXSS - SLAC. June 18, 2009

  12. O/P Profile and Spectral Distribution FEL output builds up from spontaneous emission (photon noise) => SASE – ‘Self Amplified Spontaneous Emission’ Corrected XUV Spectrum Raw XUV Spectrum UXSS - SLAC. June 18, 2009

  13. Part 2 - Experiments on dilute targets with FLASH Motivations 1. ‘FLASH’ Characterisation 2. Demonstration Experiments 3. Future (Path-finding) UXSS - SLAC. June 18, 2009

  14. Atoms in Intense XUV + Optical (Ti-Sapphire - 800/400 nm) fields Photoionization of rare gas atoms dressed by intense optical fields Summary of AMOP@FLASH http://hasylab.desy.de/science/user_collaborations/amopflash Photoionization Experiments with the Ultrafast XUV Laser FLASH 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 (2009) UXSS - SLAC. June 18, 2009

  15. FLASH NIR/UV and XUV Beam Layout PG2 BL1 BL2 visible laser light BL3 UXSS - SLAC. June 18, 2009

  16. Two colour ATI/ Laser Assisted PES 15.76 eV Ar(IP) Superposition of visible and XUV pulses in a noble gas jet Schins et al. PRL 73, 2180 (1994) Electron Spectrometer hwir =1.55eV XUV NIR (800 nm) fs laser pulse Sideband intensity very sensitive to XUV-IR pulse area overlap. - Cross Correlation… Gas Jet E.S. Toma et al. PRA 62 061801 (2000)

  17. Cross (IR-XUV) correlation using HH 20 15 electron kinetic energy /eV 10 5 -60 -40 -20 0 20 40 60 Delay / fs Low field regime: Int(IR) ≈ 1011 W/cm2 G(sideband)2 = G(IR)2 + G(VUV)2 XUV-IR Cross-Correlation e- H21 IR H19 H17 (26eV) 15,76 eV Ar+ 3p5 VUV Ar 3p6 DT (laser) = 30fs M Meyer et al., PRA 69 051401(R) (2004)

  18. 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)

  19. Two colour ATI/ Laser Assisted PES Sideband number/intensity depend strongly on XUV/NIR overlap  by comparison with theory we are able to determine relative time delay to better than 100 fs 550 fs 1. New ultrafast XUV-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) 94 144102 (2009) P. Radcliffe, et al., Nucl. Instr. and Meth. A 83, 516-525 (2007) P. Radcliffe, et al., APL 90 131108 (2007)

  20. 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)

  21. Two colour ATI - Z Scaling Resonances  b ! 800 nm Ti-Sa 1.55 eV/ 120 fs FLASH h ~ 93 eV 20 J/pulse Low b ! UXSS - SLAC. June 18, 2009

  22. Two colour ATI - Z Scaling Intensity ratio of n = SB1/SB2( sidebands) - Model vs Experiment FEL Wavelength: 13.9 nm Fitted 800 nm intensity ~ 5 x 1011 W.cm-2 Experiment ‘Soft Photon’ UXSS - SLAC. June 18, 2009

  23. 2 colour ATI - FEL Wavelength Scaling FEL + LASER (800 nm) Sideband Ratios - Comparison of Soft Photon Approximation with Experiment where UXSS - SLAC. June 18, 2009

  24. 2 colour ATI - Optical Intensity Scaling Ne: High dressing field sideband distribution UXSS - SLAC. June 18, 2009

  25. 2 colour ATI - Optical Intensity Scaling Ne: ‘Toy’ SFA Code / Asymmetry in sideband distribution Ne: Simulation hFEL = 46 eV UXSS - SLAC. June 18, 2009

  26. 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)

  27. 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)

  28. Atomic Dichroism in Inner-Shell ATI - Kr FLASH: 13.7 nm, 10-20 fs, 20µJ OL: 800nm, 4ps, 6 x 1011 W/cm2 SPA works well for both valence (4p) and inner shell (4s) electrons. Work in progress to determine s/d ratio from the above….. UXSS - SLAC. June 18, 2009

  29. Atomic Dichroism in Ionic ATI - Ne+ Ne - Sequential Ionization 1. Ne (2p61S) + h (46 eV)  Ne+(2p52P) + e-(~34 eV) 2. Ne+ (2p52P) + h (46 eV)  Ne2+(2p43P/1D) + e-(~ 25 eV) hFEL = 46 eV ‘Coherent’ blend of 3P and 1D sidebands…. ‘Isolated 3P 1st and 2nd sidebands…. ‘Work in progress’ - but we can begin to think about studying isonuclear trends……. UXSS, SLAC - June 18 2009

  30. Atomic Dichroism in Ionic ATI - Ne+ b =0.005 b =0.003 SPA fits in progress… Core ‘2S+1LJ’ effects ? a + b Cos2() b =0.019 b =0.008 b =0.005 UXSS, SLAC - June 18 2009

  31. Two Colour X-ray+NIR Expts @ LSLS Collaboration: J. Bozek, A. Cavalieri, R. Coffee, J. Costello, S. Duesterer, R. Kienberger, M. Meyer, L. DiMauro & T. Tschentscher - LCLS, DESY, MPQ, DCU, Orsay & Ohio Few Femtosecond Photo and Auger Electron Dynamics in Strong Optical Fields Experimental Plan for Fall 2009 and Proposed for 2010……. Chirped Pulse Laser Assisted Auger Decay - CPLADD Single Shot Atomic Streak Camera - SSASC UXSS, SLAC - June 18 2009

  32. Two Colour X-ray + NIR Expts @ LSLS Chirped Pulse Laser Assisted Auger Decay - CPLADD Target:Ne LCLS:830-850 eV ~50 fs Laser:800 nm or 650-1100 nm ~200 fs Chirped No Chirp 1. Auger electron: Linewidth independent of FEL BW (e.g., Ne - 0.23 eV) 2. Auger electron pulse mimics LCLS pulse: Electron replica  photocathode 3. No Chirp: Auger electron bunch exchanges photons with single carrier hL 4. Chirped: Auger bunch exchanges photons with time-varying carrier energy- Ergo different parts of the bunch experience different energy shifts - (time  energy) => sideband shapeX-ray pulse profile……… UXSS, SLAC - June 18 2009

  33. Two Colour X-ray+NIR Expts @ LSLS Single Shot Atomic Streak Camera - SSASC Target:Rare gas,LCLS: >800 eV, ~1 - 4 fs, Laser:OPA (2000 nm, ~ 7 fs), c. With dressing field (peak value) => shifted, no broadening….. a. Without dressing field => unshifted, no broadening….. b. With dressing field (zero crossing) => unshifted, broadened….. 1. Electron bunch must replicate ultrashort X-ray pulse……. 2. Electron bunch duration must be shorter than one half cycle of the OPA dressing field (~ 3fs)…… 3. Photoelectron energy shift follows the electric field of the IR dressing laser….. 4. In the zero field crossing case the electron pulse is streaked in both directions resulting in a broadened but unshifted electron line - the electron linewidth will depend on the electron (X-ray) bunch length (case ‘b’) 5. On the other hand, if the electron bunch falls on the carrier peak, all parts of the bunch ‘feel’ approximately the same dressing field, ergo the electron bunch will be shifted by a constant energy (case ‘c’) 6. Postprocessing - retrieve zero crossing cases to determine LCLS pulse width distribution (< 1 to 4 fs ?) UXSS, SLAC - June 18 2009

  34. 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 order PT & SPA agree 3. Beyond He we really need to measure angular distributions to try to unravel the ‘l’ channels (Kr 4s ?) 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) Is there really value in going beyond SPA ? Does the residual ion core atomic structure really matter ? (Ne+) LCLS will test the limits of UF X-ray techniques…. UXSS, SLAC - June 18 2009

  35. Atoms in Intense XUV Fields Part 3. Few XUV Photon Ionization UXSS, SLAC - June 18 2009

  36. FLASH Offers………… High intensity - 100J/10fs/10m ~ 1016 W/cm2 Interaction with matter Expect few photon non-linear photoionization processes….. High (XUV) photon energy- 50 - 200 eV Keldysh -  where UXSS, SLAC - June 18 2009

  37. Keldysh - Ionization Regime Multiphoton Ionization Tunnel Ionization Field Ionization >>1  ~ 2  <<1 Atoms in Intense XUV Fields Intensity/ Wavelength Photon Energy UXSS, SLAC - June 18 2009

  38. Keldysh - Ionization Regime Multiphoton Ionization Tunnel Ionization Field Ionization >>1  ~ 2  <<1 Ti-Sapphire in the NIR Non-Pertubative (TI) Regime FLASH in the XUV - Pertubative (MPI) Regime: So these non linear photoionization processes will involve predominantly few photons and potentially few electrons UXSS, SLAC - June 18 2009

  39. Xe ionization in intense XUV fields Sorokin, Richter et al., PTB, PRL 2008 UXSS, SLAC - June 18 2009

  40.  4d photoionization @ h = 93 eV FEL only. h ~ 93 eV Xe + h Xe+ + e- Intensity scaling... Weakest field… Replace Ion TOF by MBES – photoelectron spectrosopy UXSS, SLAC - June 18 2009

  41.  4d two photon direct ionization FEL only. h ~ 93 eV Xe + 2h Xe+ + e- Interpretation proving a challenge as ionization and excitation balance changes on a sub-fs timescale (and spatially)……. Must not ignore 4p- Auger processes also ! UXSS, SLAC - June 18 2009

  42. Part 4. Next Steps 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 UXSS, SLAC - June 18 2009

  43. Kr (3d94d) 2 Photon Resonance Auger Experiment. June 15 (2009) MLM - 3 degree incidence……. Kr+ 3d92D5/2 92.0eV 4d Auger Kr: 3d104s24p6 + 2h (46 eV) 3d94s24p64d  1. Kr+: 3d104s24p44d +el (~60 eV) 2. Kr+: 3d104s24p5 + el’ (~75 eV) XUV 46.1 eV Kr+ 4p44d, 5d Kr+ 4p5 Kr 3d10 4s2 4p6 UXSS, SLAC - June 18 2009

  44. Kr (3d94d) 2 Photon Resonance Auger Experiment. June 15 (2009) MLM - 3 degree incidence……. Kr+ 3d92D5/2 92.0eV 4d Auger XUV 46.1 eV Kr+ 4p44d, 5d Kr+ 4p5 FLASH June 18, ca. 5.30 am CET Duesterer, Li & Richardson…… Kr 3d10 4s2 4p6 UXSS, SLAC - June 18 2009

  45. Experiments post-upgrade Upgrade atFLASH- Optical Parametric Amplifier - (fs OPA) Laser coupling/spectroscopy of autoionization states UXSS, SLAC - June 18 2009

  46. 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) UXSS, SLAC - June 18 2009

  47. 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 UXSS, SLAC - June 18 2009

  48. 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: FLASH - seeding, fs jitter, angle resolved PES,… X-rays - LCLS/XFEL/SPRING-8/NLS 5. The future is bright and the XUV & X-ray are even more exciting (now) (J-P Connerade, ICL) UXSS, SLAC - June 18 2009

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