Multicolor Spectroscopy with Free Electron Lasers

1. Free Electron Laser based Multicolor Spectroscopy C. Masciovecchio Elettra - Sincrotrone Trieste, Basovizza, Trieste I-34149 • Introduction to FERMI Free Electron Laser • The Experimental End-Stations • EIS program (TIMEX & TIMER) • MULTICOLOR Spectroscopy

2. Why Free Electron Lasers ? 1 A 10keV Synchrotron radiation HPE FELs 1 nm 1keV HHG in gases Plasma lasers 10nm 100eV Peak brilliance= photons/s/mrad2/mm2/0.1%bandwidth LPE FELs 100 nm 10eV Conventional lasers 1eV 1μm Pulse Duration 10fs 1ps 1ns 10ps 100fs 1fs 100ps Imagingwith high Spatial Resolution (~ l): fixed target imaging, particle injection imaging,.. Dynamics: four wave mixing (nanoscale), warm dense matter, extreme condition, .... Resonant Experiments: XANES (tunability), XMCD (polarization), chemical mapping, ……

3. SASE vs Seeded x 105 Electron bunch time Optical pulse L. H. Yu et al., PRL(2003)

4. Dt < 100 fs Flux ~ 1013ph/pulse E ~ 10 - 500 eV Total Control on Pulse Energy Time Shape Polarization E. Allaria et al., Nat. Phot. (2012); Nat. Phot. (2013)

5. The Experimental Hall EIS(Elastic & Inelastic Scattering) C. Masciovecchio et al., J. Synch. Rad. (2015) TIMER TIMEX F. Capotondi et al., J. Synch. Rad. (2015) LDM(Low Density Matter) DIPROI(DIffraction & PROjection Imaging) MagneDYN(Magnetic Dynamics) TeraFERMI(THz beramline)

6. The Experimental Hall DIPROI TIMEX LDM TIMER

7. DIPROI Highlights Ultrafast Magnetic Dynamics Co/Pt ML Controlling ultrafast demagnetization using localized optical excitation C. von Korff Schmising, S. Eisebitt et al, submitted

8. DIPROI Highlights A. Martin et al. (2014) X-ray holography with customizable reference Ideal FTH  overcoming restriction due to the reference wave single-shot imaging Conjugate-gradient algorithm to recover the image FTH with an almost unrestricted choice for the reference Known reference Longitudinal coherence matters!! Sample Hologram refined with RAAR phase retrivial Diffraction

9. Pump & Probe • The pump pulse produces a change in the sample • stimulate a chemical reaction • non-equilibrium states • extreme thermodynamic conditions • ultrafast demagnetization • coherent excitations • .................. Signal that is monitored by the probe pulse GaAs Jitter ~5 fs WORLD RECORD !! M. Danailov et al., Opt. Express (2014)

10. Elastic and Inelastic Scattering (EIS) The Sample Side Short pulses with very high peak power Dt ~ 100 fs ; Peak Power ~ 5 GW ; E ~ 100 eV Non-equilibrium distribution of electrons What happens to the Sample? Converge (electron-electron & electron-phonon collisions) to equilibrium (Fermi-like) The intensity of the FEL pulses will determine the process to which the sample will undergo: simple heating, structural changes, ultrafast melting or ultrafast ablation interior of large planets and stars TIMEX TIMER

11. TIMEX TIme-resolved studies of Matter under EXtreme and metastable conditions F. Bencivenga et al., (2014) Pump & Probe FEL Ti

12. Pump & Probe on Germanium Pump 800 nm Probe FEL Upon the absorption edge (Fermi level) the spectroscopy is sensitive both to the Fermi function smearing (red curve) and to the shift of the edge due to the metallization of the sample (blue curve) 20 mm E. Giangrisostomi et al., in preparation

13. Q (q) q 2 10 IXS BLS IUVS 1 w = cs·Q 10 BL30/21 0 10 -1 10 w (meV) = 7000 m/s INS BL10.2 V -2 10 = 500 m/s V -3 10 nano-scale macro-scale atomic-scale -4 10 -3 -2 -1 0 1 2 10 10 10 10 10 10 Q ( nm -1 ) EIS - TIMER TIMER TIME-Resolved spectroscopy of mesoscopic dynamics in condensed matter Challenge: Study Collective Excitations in Disordered Systems in the Unexploredw-Q region Unsolved problems in physics Determination of the Dynamic Structure Factor: S(Q,w)

14. Why disordered systems at the nanoscale ? The nature of the vibrational dynamics in glasses at the nanoscale is still unclear (V-SiO2) M. Foret et al., PRL 77,3831 (1996)  They are localized above ~ 1 nm-1 P. Benassiet al., PRL 77,3835 (1996)  Existence of propagating excitations at high frequency F. Setteet al., Science 280,1550 (1998)  They are acoustic-like G. Ruocco et al., PRL 83, 5583 (1999)  Change of sound attenuation mechanism at 0.1-1 nm-1 B. Ruffle´ et al., PRL 90, 095502 (2003)  Change is at 1 nm-1 C. Masciovecchio et al., PRL 97,035501 (2006) Change is at 0.2 nm-1 W. Schirmacheret al., PRL 98,025501 (2007)  Model agrees with Masciovecchio et al. B. Ruffle´ et al., PRL 100,015501 (2008)  Shirmacher model is not correct G. Baldiet al., PRL 104,195501 (2010)  Change is at 1 nm-1 PRL 112, 025502 (2014); Nat. Comm. 5,3939 (2014); PRL 112,125502 (2014) Fundamental to understand the low temperature anomalies in glasses

15. 2 10 IXS BLS 1 10 IUVS 0 Esignal 10 -1 10 (meV) = 7000 m/s INS w Q(l,q) V -2 10 = 500 m/s Epump V q -3 10 -4 10 -3 -2 -1 0 1 2 10 10 10 10 10 10 Epump -1 Q ( nm ) Eprobe EIS beamline - TIMER Solution: Free Electron Laser basedTransient Grating Spectroscopy F(Q,t) European Research Council Funded Grant: 1.8M€

16. F(Q,t) (a.u.)  region Thermal region Sound waves region t (ps) S(Q,w) (a.u.) w (meV) The Spectrum Optical absorption  Temperature Grating Time-dependent Density Response (driven by thermal expansion) S(t)  ( cost – F(Q,t)) S(t) Glycerol T=205 K H2O 2 nm-1 Gaussian-like time profile

17. Typical Infrared/Visible Set-Up M 1 Probe laser beam Delay Line DM 2=21 Excitation laser beam Phase Control (Heterodyne) Beam stop (Homodyne) Neutral Filter (Heterodyne) Eex1 EL APD M Epr Sample DOE: Phase Mask Eex2 Es (Homodyne) EL+Es (Heterodyne) AL2 AL1 Challenge: Extend and modify the set-up for UV Transient Grating Experiments

18. TIMER Layout 3rd harmonic (probe) 2θ Beam waist Delay line: 4 ML mirrors (abs 1st, reflect 3rd harm), time delays up to ~ 3 ns θB “Original beam” Vertical Pump1 Pump2 1st harmonic (pump) Horizontal FEL pulse:1st and3rd harmonic (λ3 = λ 1/3) Probe @ sample position Plane Mirrors “beam splitters” Vertical Focusing mirror Horizontal R. Cucini et al et al., NIMA (2011)

19. -FEL1 -FEL2 FEL Transient Grating Experiments on V-SiO2 Detector (EUV-Vis cross-corr.) Si3N4 reference sample M0 M1 FEL1 Beamstops θB M2 FEL2 λopt ΔtFEL-FEL= ± 0.5 ps at 2θ = constant M0 M1 F. Bencivenga et al., NIMA (2010) R. Cucini et al., NIMA (2011) R. Cucini et al., Opt. Lett. (2011) F. Casolari et al., Appl. Phys. (2014) M. Danailov et al. Opt. Express (2014) R. Cucini et al., Opt. Lett. (2014) 2θ M2

20. kfout CCD FEL Transient Grating Experiments on V-SiO2 F. Bencivenga et al., Nature 2015 M0 θ M1 kFEL,1 lFEL = 27.6 nm 2θ 2θ Permanent Grating after 1k-shots Optical path difference < λFEL θB M2 kFEL,2 λopt kopt

21. Transient Grating Experiments on V-SiO2 Hyper - Raman modes due to coupled tetrahedral rotations Raman modes due to tetrahedral bending Acoustic-like excitations

22. kfout CCD Heterodyning with FEL Heterodyning is a signal processing technique invented in 1901 by R. Fessenden Time independent local field I [arb. units] λopt kopt

23. CB VB w1k1 ω2 ω3 ωout ω1 Δt w3 k3 atom-A w2 k2 atom-B Four Wave Mixing at FEL’s w4 k4 Transient grating is one of Four Wave Mixing techniques Coherent Antistokes Raman Scattering (CARS) S. Tanaka & S. Mukamel PRL (2002) • Charge and Energy transfer are fundamental for: • Metal complexes • Organic solar cells • Metal oxides nanoparticles • Thin heterostructures • ……… • ……… Measure the coherence between the two different sites  it makes possible to chose where a given excitation is created, as well as where and when it is probed delocalization of electronic states and charge/energy transfer processes

24. Multiple pulse configurations Mahieu et al. Opt. Express (2013) Multiple pulses can be generated by double pulse seeding Temporal separation between 25-300 and 700-800 fs. Shorter separations are accessible via FEL pulse splitting. Larger separations require the split & delay line. Spectral separation 0.4-0.7% (E. Allaria et al., Nat. Comm 2013) time gain bandwidth Spectral separation 2-3% or much larger if the two radiators are tuned at different harmonics (Sacchi et al., in preparation) spectrum spectrum RAD2 gain bandwidth time time Two (almost) temporally superimposed pulses at harmonic wavelengths of the seed. They are correlated in phase that can be controlled with the phase shifter (K. Prince et al., submitted) MOD gain bandwidth MOD gain bandwidth RAD1 gain bandwidth spectrum spectrum

25. Θprobe Ti grating Θpump t l1pump l2

26. Pump & Probe on Silicon Pump FEL Probe FEL E. Principi et al., in preparation P. F. McMillan et al., Nature (2005)

27. LDM Highlights Coherent control at the attosecond time scale K. Prince et al., submitted Interference effect among quantum states using single and multiphoton ionization C. Chen et al., PRL (1990) Intensity = | M1 + M2(ϕ)| = | M1|2 + |M2(ϕ)|2 + 2 Re(M1 M2(ϕ)) Use of first (62.974 eV ) and second harmonic on 2p54s resonance of Ne Change of the phases among the two harmonics ‘invented’ by Allaria et al., Signal detected as function of phase on the VMI detector Control of the phase among the two pulses!

28. Conclusions

29. Conclusions • Charge transfer dynamics in metal complexes • Charge injection and transport in metal oxides nanoparticles • Vibrational modes in Glasses • Charge Density Wave • Quasiparticle diffusion (Polarons) • Sound velocity in Graphene A. Föhlisch G. Knopp T. Scopigno G. Monaco K. Nelson M. Chergui

30. Acknowledgments M. Danailov M. Zangrando F. Parmigiani M. Kiskinova L. Giannessi C. Callegari A. Battistoni M. Manfredda F. Capotondi P. Finetti R. Cucini M. Di Fraia A. Gessini E. Pedersoli R. Richter O. Plekan F. Bencivenga K. Prince R. Mincigrucci E. Principi M. Coreno E. Giangrisostomi