X-Rays and Materials A Vision of the Future Joachim Stöhr Stanford Synchrotron Radiation Laboratory

In $$$$$'s Information technology: 800 Billion Chemical Industry: 400 Billion Semiconductors: 80 Billion Magnetic materials: 25 Billion Pharmaceutical industry: 220 Billion Biotech Industry: 30 Billion The big $$$ Picture: US Gross Domestic Product: $10 Trillion Modern materials are complex – studies require sophisticated techniques

Present: Size > 0.1  m, Speed > 1 nsec Future: Size < 0.1  m, Speed < 1 nsec Ultrafast Nanoscale Dynamics

Growth of X-Ray Brightness and Magnetic Storage Density

Why X-Rays? - Chemical Sensitivity Core level shifts and Molecular orbital shifts Stöhr et.al

Polarization Dependence Normal Incidence Grazing Incidence Normalized Intensity (a.u.) Photon Energy (eV) F8 22°C C F C O C

Magnetic Spectroscopy and Microscopy

Real Space Imaging X-Rays have come a long way……

The Future: PEEM3 PEEM2PEEM3 nm nm Resolution50 nm< 5 nm (1% transmission) 50 nm Resolution Relative photon flux 120 Relative Flux density1>1000 Source / bendEPU (arbitrary) Polarization PEEM2 on BL Photoemission Electron Microscopy – PEEM at ALS

4.0.3 PEEM3 Microscope - total electron yield imaging - no LEEM mode (as in SMART)

Resolution vs Transmission

 m [010]   NiO XMLD Co XMCD Spectromicroscopy of Ferromagnets and Antiferromagnets AFM domain structure at surface of NiO substrate FM domain structure in thin Co film on NiO substrate H. Ohldag, A. Scholl et al., Phys. Rev. Lett. 86(13), 2878 (2001).

Non Resonant X-Ray Scattering Relative Intensity: (h  / mc 2 ) 2 Relative Intensity: 1 h ~ 10 keV, mc 2 = 500 keV

Kortright and Kim, Phys. Rev. B 62, (2000) Fe metal – L edge

Fe Resonant Magnetic Soft X-ray Scattering M e e’e’ 2 f n  e'  e F n (0)  i(e'  e)  M n F n (1) chargemagnetic -XMCD = f 1 + i f 2 Note: at resonance f 1 = 0 where F n (i) are complex Kortright and Kim, Phys. Rev. B 62, (2000)

Small Angle Scattering Coherence length larger than domains, but smaller than illuminated area Speckle Coherence length larger than illuminated area Incoherent vs. Coherent X-Ray Scattering scattering vector q (  m -1 ) scattering vector q (  m -1 ) information about domain statistics true information about domain structure

Present Pump/Probe Experiments 330 ns 50 ps X-Ray pulse Laser pulse Pump: Laser Probe: delayed photon pulse Vary the delay between laser and x- ray pulses  Can also produce current pulses

Storage rings Single pass linear colliders Development of High Energy Physics and X-Ray Sources HEP SR Single pass linacs Free electron lasers (FELs) Energy recovery linacs (ERLs) -- From storage rings to linacs --

X-Ray Brightness and Pulse Length X-ray brightness determined by electron beam brightness X-ray pulse length determined by electron beam pulse length Storage ring Emittance and bunch length are result of an equilibrium typical numbers: 2 nm rad, 50 psec Linac beam can be much brighter and pulses much shorter – at cost of “jitter” Linac Normalized emittance is determined by gun Bunch length is determined by compression typical numbers: 0.03 nm rad, 100 fs

SASE gives 10 6 intensity gain over spontaneous emission FELs can produce ultrafast pulses (of order 100 fs)

L INAC C OHERENT L IGHT S OURCE 2 Km 0 Km 3 Km

Based on single pass free electron laser (FEL) Uses high energy linac (~15 GeV) to provide compressed electron beam to long undulator(s) (~120 m) – 200 fs or less Based on SASE physics to produce 800-8,000eV (up to 24KeV in 3 rd harmonic) radiation photon/shot Analogous in concept to XFEL of TESLA project at DESY Planned operation starting in 2008 Concepts of the LCLS:

From Molecules to Solids: Ultra-fast Phenomena Chemistry & Biology: H 2 O  OH + H about 10 fs time depends on mass and size Condensed Matter: typical vibrational period is 100 fs Speed of sound is 100 fs / Å - coherent acoustic phonons H S 90 o spin precession time 10 ps for H = 1 Tesla Fundamental atomic and molecular reaction and dissociation processes Fundamental motions of charge and spin on the nanoscale (atomic – 100nm size) Note in quantum regime: 1 eV corresponds to fluctuation time of 4 fs

transversely coherent X-ray pulse from LCLS sample X-Ray Photon Correlation Spectroscopy Using Split Pulse In picoseconds - nanoseconds range: Uses high peak brilliance sum of speckle patterns from prompt and delayed pulses recorded on CCD splitter variable delay Contrast Analyze contrast as f(delay time)

Transmission X-ray Microscope Reconstruction from Speckle Intensities  5  m (different areas) Single shot Imaging by Coherent X-Ray Diffraction Phase problem can be solved by “oversampling” speckle image S. Eisebitt, M. Lörgen, J. Lüning, J. Stöhr, W. Eberhardt, E. Fullerton (unpublished)

Magnetization Temperaturet = (T-T c ) / T c TcTc Spin Block Fluctuations around Critical Temperature T < T c T  T c T > T c

Structural Studies on Single Particles and Biomolecules Proposed method: diffuse x-ray scattering from single protein molecule Neutze, Wouts, van der Spoel, Weckert, Hajdu Nature 406, (2000) Implementation limited by radiation damage: In crystals limit to damage tolerance is about 200 x-ray photons/Å 2 For single protein molecules need about x-ray photons/Å 2 (for 2Å resolution) Lysozyme Calculated scattering pattern from lysozyme molecule Conventional method: x-ray diffraction from crystal

X-Ray Diffraction from a Single Molecules Just before LCLS pulse Just after pulse A bright idea: Use ultra-short, intense x-ray pulse to produce scattering pattern before molecule explodes Long after pulse The million dollar question: Can we produce an x-ray pulse that is short enough? intense enough?

X-FELs will deliver: unprecedented brightness and femtosecond pulses Understanding of laser physics and technology well founded FELs promise to be extraordinary scientific tools Applications in many areas: chemistry, biology, plasma physics, atomic physics, condensed matter physics Summary

The End