New Science with

Next Generation Light Sources

F. J. Himpsel

BESAC, February 26, 2009

Identify new science and the photon attributes of

next generation light sources required to carry it out, such as:

• Energy range (from vacuum UV to hard X-rays)

• Coherence

• Time resolution (femtosecond regime)

• Brilliance (average, peak)

• Polarization (circular, linear)

Charge 3 from BESAC

to the New Era

Committee

• Identify connections between major research opportunities

and the capabilities of next generation light sources.

• Find “killer applications” that could become scientific

drivers.

• Emphasize energy-related research and life sciences.

• Consider the VUV to X-ray range and include both

accelerator- based light sources and laser-based sources.

• Do not choose a specific light source design, consider only the photon attributes required for the most promising research.

• Strong coupling of theory and experiment.

Charge to the Participants of the Photon Workshop

Program of the Photon Workshop

100 Participants, chaired by W. Eberhardt and F. J. Himpsel

• Overview talks:

Energy (Crabtree, ANL) Life Sciences (Moffat, Chicago)

• Next Generation Light Sources:

Free Electron Lasers (Pellegrini, UCLA)Energy Recovery Linacs (Hofstaetter, Cornell)High Harmonic Lasers (Sandner, Germany)Next Generation Storage Rings (Martensson, Sweden)

• Breakout Groups: Extensive discussions, write-up of highlights (1½ days)

Breakout Groups

Coordinator:

1. Nanoscale Electrons and Spins Hermann Dürr (Berlin)

2. Correlated Electrons Z. X. Shen (Stanford)

3. Catalysis and Chemistry Robert Schlögl (Berlin)

4. Nano-Materials for Energy Applications Rick Osgood (Columbia)

5. Life Sciences Janos Kirz (Berkeley)

6. Atomic and Molecular Physics Nora Berrah (West.

Michigan)

7a. Matter under Extreme Environments Rus Hemley (Carnegie Inst.,

DC)

7b. Environmental Science, Earth Science Gordon Brown (Stanford)

8. Novel Structural and Electronic Materials Julia Phillips (Sandia)

9. Cross-Cutting Issues John Hemminger (Irvine)

Generated an extensive number of scientific opportunities

(collected in Section 4, the largest section)

Findings

• Five Cross-Cutting Challenges

• Three Stages of Difficulty

Three Stages of Difficulty

Stage A:

• Widest range of applications, largest user community

• Least aggressive in terms of machine requirements

(but clearly beyond available light sources)

Stage B:

• Novel experiments, demanding a new kind of light source

• Widespread applications, many potential users

• Could become the centerpiece of next generation light

sources

Stage C:

• Most aggressive, highest risk, but also high potential payoff

The Sweet Spot: Stage B

The active Fe6Mo center of nitrogenase,

Nature’s efficient way of fixing nitrogen:

• Resolve the chemical reaction steps in time.

• What are the resulting structural changes ?

• Determine the charge flow by spectroscopy.

Comparison with the NSF Studyhttp://www.nsf.gov/attachments/109807/public/LightSourcePanelFinalReport9-15-08.pdf

• Two new scientific frontiers, similar to our two bullets (except for reverse order, technique instead of scientific challenge)

• Developed independently

The Science Case:

The Berkeley Workshop Report

https://hpcrd.lbl.gov/sxls/Workshop_Report_Final.pdf

“No light source in existence, under construction, or on the drawing board can deliver the beams required for the cutting edge science described in this document.”

Scientific areas addressed by new light sources:

(1) Chemical Physics

(2) Atomic, Molecular, and Optical Physics

(3) Magnetization and Spin Dynamics

(4) Correlated Materials

(5) Exploration of Nanoscale Dynamics and Complexity

The White Paper from the DOE Light Sourceshttp://www-ssrl.slac.stanford.edu/aboutssrl/documents/future-x-rays-09.pdf

Scientific drivers:

Consider the Traditional Split between “UV” and X-ray Light Sources

Gratings Crystals

Electronic Structure Atomic Structure

Lithography, Nanostructures

PhotonEnergy

Wave-length

10eV 100eV 1keV 10keV

10nm100nm 1nm 1Å

ValenceElectrons

Core Electrons Sharp Deep

ProteinCrystallo- graphy

Proteomics

Magnetis

m

Environme

nt

Chemical Information from X-ray Absorption Spectroscopy

Core to Valence Transitions : 1s 2p (*, *) , 2p 3d, …

Sharp levels (<1keV) for bond orbitals Deep levels (>1keV) for dilute species

BioCatalysts

Examples for New Possibilities

Organic Molecules with a Transition Metal as Active Center

(LEDs, Solar Cells, Enzymes = Bio-Catalysts)

Detect oxidation state, spin state, ligand field for one Fe atom.

What Happens during a Photochemical Reaction ?

X-ray absorption spectra of a solvated organic Fe complex for the low-spin ground state (blue) and an excited high-spin state

(red).

These measurements on the 100 picosecond time scale provide information about spin excitations and their lifetime. To learn about

structural dynamics one needs 100 femtosecond (fs) time resolution, and

for electronic excitations a few fs . That is only possible with next

generation light sources.

Spatially Resolved Catalytic Reactions

Want this chemically resolved Chemically resolved, but insufficient spatial resolution

Fischer-Tropsch process for con-verting coal to liquid fuel.

Fast Switching of Spins

Surprisingly-fast switching of spins in the femtosecond range. How did the angular momentum get absorbed ?

Low-power electronics: Switching of spins requires little energy, but can it be fast? The limit is given by the uncertainty relation.

Proteins in Action

Can observe slow recombination, but not yet the fast initial biochemical reaction.

Time-evolution of a protein structure after stimulating the Fe atom in the heme.

Spectroscopy of Isolated Nanoclusters with Well-Defined Atomic Structure

Control materials atom by atom.

The energy gap between the highest occupied and lowest unoccupied energy level of mass-selected atomic clusters.

Need higher photon energy to see all the other energy levels.

Towards Spectroscopy of an Isolated Nano-Object

Reach atomic precision in

nanotechnology.

Optical spectra of self-assembled quantum dots show a broad continuum due to the size distribution. Selecting fewer dots with

smaller apertures reveals the discrete line spectrum expected from an isolated dot ( “artificial atom”).

Need higher photon energy to access all levels, including core levels.

Conclusions

Two science drivers (“killer-apps”) for new light sources are identified

which combine the deepest science impact with the broadest user base:

• Femtosecond time resolution opens completely new

territory where atoms can be followed in real time and electronic excitations can be resolved down to their intrinsic time scale.

• Sub-nanometer spatial resolution opens the length scale

where quantum confinement dominates electronic behavior and where catalytic activity begins. Spectroscopy

of individual nanometer-scale objects rather than

conglomerates will eliminate blurring of the energy levels

induced by the size and shape distribution and thereby

reveal active sites in catalysis and the traps where electrons are lost in photovoltaics.

Backup Slides

Cross-Cutting Challenges: Stage A

1. Designing Materials, Controlling Processes:

The Synthesis-Analysis-Prediction-Loop

• Materials: Complex materials with correlated electrons, operating

devices, batteries, supported catalysts, organic conductors for

photovoltaics, lighting, quantum-engineered cluster assemblies

• Interfaces: In-situ, buried, nano-structured, bio-inorganic, sequestration,

grain boundaries in solar cells and superconductors, damage in nuclear

reactor materials

• Catalysts: For artificial photosynthesis, splitting water, in realistic

situations (presence of gases, liquids)

• Static measurement (time-resolved in 2., spatially-resolved in 3., both

in 5.)

2. Real Time Evolution of Chemical Reactions, Movements of Electrons and

Spin

• Photovoltaics, Photosynthesis: Harvest sunlight efficiently and

economically

• Reactions at defects: Loss of (photo)electrons, radiation damage, in real

time

• Spintronics: How fast can one switch spins

• Chemical reaction mechanisms: Catalysis, biochemistry in real time

3. Individual Nano-Objects

• Atomic clusters: Tailoring new forms of matter with atomic precision

• Nanocrystals: Beating the size distribution

• New materials: Find the electronic structure of a small crystallite

• Large protein assemblies: From proteomics to cells

Cross-Cutting Challenges: Stage B

4. Statistical Laws of Complex Systems

• Fluctuations of floppy spins and soft materials at the nanometer scale

• Utilize the full coherence and high degeneracy of a laser

• Utilize a shaped pulse to reach the minimum uncertainty product

5. Small and Fast

• Resolve the coupled motion of electrons and nuclei

• Imaging of elementary chemical reactions at the molecular level

• Electrons travel nanometers in femtoseconds, challenging the limits of

combined spatial and temporal resolution

Cross-Cutting Challenges: Stage C

Measuring S(q,) by Resonant Inelastic X-ray Scattering (RIXS)

• Complete characterization of a solid

• Find the boson that pairs electrons in high temperature superconductors

• Need 10x better energy resolution and statistics to be relevant

RIXS data from a high temperature superconductor

Coherent Imaging

Coherent diffraction from a yeast cell Reconstruction

• 3D

• Chemical image, phase image, optimum use of photons (min. damage)

• Beyond protein crystallography towards larger objects, proteomics

Imaging Wave Functions

• Obtain the wave function of electrons in nano-objects

• Transfer lensless imaging techniques from photons to electrons

• Needs strong coupling to theory to describe multiple electron scattering

Angle-resolved photoemission data, transformed from reciprocal space to real space.

Speckle pattern of Co:Pt film at = 1.6 nm

Combine Coherent Diffraction with Time Resolution

Reveal Simple Statistical Laws of Complex Systems

Small and Fast

• Ultrafast optoelectronics via plasmonics

• Electron velocity in metals nm/fs

• Electron lifetime in metals 10 fs mean free path 10 nm

Light trapped in nanometer-sized Ag structures during femtoseconds via localized plasmons

Interference Lithography

• Large-scale nano-patterning at = 13 nm (EUV lithography)

• Controlled placement of self-assembled units (dots, wires, biomolecules)

• Patterned high-density data storage media

Flat substrate + block-copolymer Patterned substrate

Size of a molecule determines linewidth, smoothness