John T. Costello

National Centre for Plasma Science & Technology (NCPST)/ School of Physical Sciences, Dublin City Universitywww.physics.dcu.ie/~jtcTwo Colour and Two Photon Ionization Processes in Intense XUV and Optical Fields at FLASHUXSS - SLAC. June 18, 2009' FLASH ' - Free Electron LASer in Hamburg

LIXAM (Orsay): D. Cubaynes, M. Meyer

Universite Paris 06 (PMC): R. Taieb, A. Maquet

DESY (Hamburg): A. Azima, S. Dsterer, 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

Queens 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.)AcknowledgementsUXSS - SLAC. June 18, 2009

DCU Intense Laser Matter ResearchAcademic 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 OLeary

Recent Postdocs: Deirdre Kilbane, Hugo de Luna, Jofre Gutieriez-Pedrogosa, Brendan Doggett, Subo Chakraborti and Jean-Rene Duclere 6 laboratory areas focussed on pulsed laser matter interactions (NIR X-ray/ 30fs 30 ns, spectroscopy/ imaging/PLD)Funded by:SFI - Frontiers and InvestigatorHEA PRTLI (Kit)IRCSET (People)EU - Marie Curie (People)UXSS - SLAC. June 18, 2009

DCU Intense Laser Matter ResearchUXSS - SLAC. June 18, 2009Research 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 SteelPLD and in-situ P-type doping of ZnO nanostructures6 laboratory areas focussed on pulsed laser matter interactions (NIR X-ray/ 30fs 30 ns, spectroscopy/ imaging/PLD)

Collaboration grew out of EU RTD Project:HRPI-CT-1999-50009

Title:X-Ray FEL Pump Probe Facility

Partners: Orsay, DCU, Lund, MBI, BESSY & DESYCollaboration - OriginUXSS - SLAC. June 18, 2009

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* !What are the USPs of XFELs in AMOP ?UXSS - SLAC. June 18, 2009*See USP No. 1

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 StepsOutline of the TalkUXSS - SLAC. June 18, 2009

Part 1 - FLASH OverviewUXSS - SLAC. June 18, 2009

UXSS - SLAC. June 18, 2009

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 J (average), 120 J (peak)Pulse duration (FWHM): 10-30 fs Peak power (fundamental): Few GWAverage power (fundamental): 0.1 W (up to 3000 pulses /sec)Photons per pulse: ~ 1013FLASH: Key Performance IndicatorsAckermann et al., Nature Photonics 1 336 (2007)

FEL output builds up from spontaneous emission (photon noise) => SASE Self Amplified Spontaneous EmissionO/P Profile and Spectral DistributionSpectral FluctuationsTemporal FluctuationsUXSS - SLAC. June 18, 2009

FEL output builds up from spontaneous emission (photon noise) => SASE Self Amplified Spontaneous EmissionO/P Profile and Spectral DistributionRaw XUV SpectrumCorrected XUV SpectrumUXSS - SLAC. June 18, 2009

Part 2 - Experiments on dilute targets with FLASH

Motivations1. FLASH Characterisation2. Demonstration Experiments3. Future (Path-finding)

UXSS - SLAC. June 18, 2009

Atoms in Intense XUV + Optical (Ti-Sapphire - 800/400 nm) fields Photoionization of rare gas atoms dressed by intense optical fields

Summary of AMOP@FLASHhttp://hasylab.desy.de/science/user_collaborations/amopflash

Photoionization Experiments with the Ultrafast XUV Laser FLASHJ 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

FLASH NIR/UV and XUV Beam LayoutUXSS - SLAC. June 18, 2009

E.S. Toma et al. PRA 62 061801 (2000)Two colour ATI/ Laser Assisted PESElectronSpectrometerGas JetNIR (800 nm) fs laser pulseXUVSuperposition of visible and XUV pulses in a noble gas jethir =1.55eVSideband intensity very sensitive to XUV-IR pulse area overlap. - Cross CorrelationSchins et al. PRL 73, 2180 (1994)

M Meyer et al., PRA 69 051401(R) (2004) Cross (IR-XUV) correlation using HHXUV-IR Cross-CorrelationH19H17 (26eV)H21Ar 3p6Ar+ 3p5VUVIRe-15,76 eVT (laser) = 30fs

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

Two colour ATI/ Laser Assisted PESP. Radcliffe, et al., Nucl. Instr. and Meth. A 83, 516-525 (2007) P. Radcliffe, et al., APL 90 131108 (2007) 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 fs550 fs1. New ultrafast XUV-modulated optical-reflectivity methods 2. TEOC. 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)

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

Two colour ATI - Z Scaling800 nm Ti-Sa1.55 eV/ 120 fsFLASHh ~ 93 eV20 J/pulseUXSS - SLAC. June 18, 2009Low Resonances !

Two colour ATI - Z ScalingFEL Wavelength: 13.9 nmFitted 800 nm intensity~ 5 x 1011 W.cm-2Intensity ratio of n = SB1/SB2( sidebands) - Model vs ExperimentSoft PhotonExperimentUXSS - SLAC. June 18, 2009

2 colour ATI - FEL Wavelength ScalingFEL + LASER (800 nm)Sideband Ratios - Comparison of Soft Photon Approximation with ExperimentUXSS - SLAC. June 18, 2009where

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

2 colour ATI - Optical Intensity ScalingNe: Toy SFA Code / Asymmetry in sideband distribution Ne: SimulationhFEL = 46 eVUXSS - SLAC. June 18, 2009

FLASH: 13.7 nm, 10-20 fs, 20JOL: 800nm, 4ps, 400J, 6 x 1011 W/cm2He 1s2 + hXUV ----> He+ 1s + pHe 1s2 + hXUV + hOL ---> He+ 1s + s, dAtomic Dichroism in Two Colour ATIStrong Polarisation Dependence of Sidebands (Low Field)Meyer et al., PRL 101 Art. no. 193002 (2008)

Atomic Dichroism in Two Colour ATI - HeLow Optical Laser Field High Optical Laser Field P. Theory: A Grum-Grzhimailo et al.SPA: A Maquet/ R TaiebMeyer et al., PRL 101 Art. no. 193002 (2008) () = 3Sd + (5Ss + Sd) cos2Ss/Sd =1.25 0.3

Atomic Dichroism in Inner-Shell ATI - KrFLASH: 13.7 nm, 10-20 fs, 20JOL: 800nm, 4ps, 6 x 1011 W/cm2SPA works well for both valence(4p) and inner shell (4s) electrons.UXSS - SLAC. June 18, 2009Work in progress to determine s/d ratio from the above..

Atomic Dichroism in Ionic ATI - Ne+Ne - Sequential IonizationWork in progress - but we can begin to think about studying isonuclear trends.UXSS, SLAC - June 18 2009Coherent blend of 3P and 1D sidebands.Isolated 3P 1st and 2nd sidebands.hFEL = 46 eV1. Ne (2p6 1S) + h (46 eV) Ne+(2p5 2P) + e-(~34 eV)2. Ne+ (2p5 2P) + h (46 eV) Ne2+(2p4 3P/1D) + e-(~ 25 eV)

UXSS, SLAC - June 18 2009Atomic Dichroism in Ionic ATI - Ne+b =0.003b =0.005b =0.019b =0.005b =0.008a + b Cos2()SPA fits in progressCore 2S+1LJ effects ?

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

Two Colour X-ray + NIR Expts @ LSLSUXSS, SLAC - June 18 2009Chirped Pulse Laser Assisted Auger Decay - CPLADDTarget: Ne

LCLS: 830-850 eV~50 fs

Laser:800 nm or650-1100 nm~200 fsNo Chirp1. Auger electron: Linewidth independent of FEL BW (e.g., Ne - 0.23 eV)2. Auger electron pulse mimics LCLS pulse: Electron replica photocathode3. No Chirp: Auger electron bunch exchanges photons with single carrier hL4. Chirped: Auger bunch exchanges photons with time-varying carrier energy- Ergo different parts of the bunch experience different energy shifts - (time energy) => sideband shapeX-ray pulse profileChirped

Two Colour X-ray+NIR Expts @ LSLSUXSS, SLAC - June 18 2009Single Shot Atomic Streak Camera - SSASCTarget: Rare gas, LCLS: >800 eV, ~1 - 4 fs, Laser: OPA (2000 nm, ~ 7 fs),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 ?)a. Without dressing field =>unshifted, no broadening..b. With dressing field (zero crossing) => unshifted, broadened..c. With dressing field (peak value) => shifted, no broadening..

Summary - Two Colour ATIDemonstrated interference free SBs to high order, polarisation control, laser and FEL parameter dependencies & SBs in atomic and ionic targetsAt low optical intensities 2nd order PT & SPA agree3.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

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

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

Atoms in Intense XUV FieldsUXSS, SLAC - June 18 2009Keldysh - Ionization RegimeMultiphoton IonizationTunnel Ionization Field Ionization>>1 ~ 2

UXSS, SLAC - June 18 2009FLASH in the XUV -Pertubative (MPI) Regime:Ti-Sapphire in the NIRNon-Pertubative (TI) RegimeSo these non linear photoionization processes will involvepredominantly few photons and potentially few electronsKeldysh - Ionization RegimeMultiphoton IonizationTunnel Ionization Field Ionization>>1 ~ 2

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

4d photoionization @ h = 93 eV FEL only. h ~ 93 eVXe + h Xe+ + e-Replace Ion TOF by MBES photoelectron spectrosopyUXSS, SLAC - June 18 2009Intensityscaling...Weakestfield

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

Part 4. Next StepsTwo Colour Resonant Photoionization ProcessesTo date we have looked only at one and two colour non-resonant processes

2. Next phase - FEL tunable and so we can explore resonant two colour processes where inner shell electrons dominateUXSS, SLAC - June 18 2009

Kr 3d10 4s2 4p6Kr+ 3d9 2D5/2 4dXUV46.1 eVAugerKr+ 4p44d, 5d 92.0eVExperiment. June 15 (2009)MLM - 3 degree incidence. Kr (3d94d) 2 Photon Resonance AugerUXSS, SLAC - June 18 2009Kr: 3d104s24p6 + 2h (46 eV) 3d94s24p64d 1. Kr+: 3d104s24p44d +l (~60 eV)2. Kr+: 3d104s24p5 + l (~75 eV)Kr+ 4p5

Kr 3d10 4s2 4p6Kr+ 3d9 2D5/2 4dXUV46.1 eVAugerKr+ 4p44d, 5d 92.0eVExperiment. June 15 (2009)MLM - 3 degree incidence. Kr (3d94d) 2 Photon Resonance AugerUXSS, SLAC - June 18 2009Kr+ 4p5 FLASH June 18, ca. 5.30 am CETDuesterer, Li & Richardson

Upgrade at FLASH - Optical Parametric Amplifier - (fs OPA)Experiments post-upgradeLaser coupling/spectroscopy of autoionization statesUXSS, SLAC - June 18 2009

Bachau & Lambropoulos, PRA (1986)Themelis, Lambropoulos, Meyer, JPB (2005) New KnobsLaser FrequencyLaser IntensityTunable Optical Laser - Laser Coupling of autoionization states - 'Autler Townes' Autoionizing Resonances - HeUXSS, SLAC - June 18 2009

FLASH - Technical DevelopmentsOPA Upgrade - 0.01 - 1 mJ/ 0.1 - 20 psSynchronisation - New FIR Undulator (THz)Seeding with HHs - Full coherenceStabilisationSynchroniosationUXSS, SLAC - June 18 2009

In Conclusion1.To date we have looked only at one and two colour non-resonant photoionization processesNow - FEL easily tunable - we can explore resonant two colour processes where inner shell electrons dominate3.Study fragmentation and ionization from vibrationally excited/selected wavepackets in simple moleculesBeyond 2009: FLASH - seeding, fs jitter, angle resolved PES,X-rays - LCLS/XFEL/SPRING-8/NLS5.The future is bright and the XUV & X-ray are even more exciting (now) (J-P Connerade, ICL)UXSS, SLAC - June 18 2009