Spatially Resolved and Atom Specific Microscopy and Spectroscopy

1. Spatially Resolved and Atom Specific Microscopy and Spectroscopy “New Characterization Tools” What can we do now that we could not do before and how will it change the world

2. Broad beam: • good statistics • average over sites • Local probe: • poor statistics • probes individual sites • Time resolution • Species specific • Spatial resolution • Site specific Complementarity of techniques Insight  NN where N = number of tools We want everything at once!

3. “Real-time” surface imaging methods • Nanoscale [“atomic” resolution] • Fast Scanning Tunneling Microscopy (STM) • Field Ion Microscopy (FIM/FEM) • Mesoscale [chemically sensitive] • Low Energy Electron Microscopy (LEEM) • Photoemission Electron Microscopy (PEEM) • Ellipsomicroscopy for Surface Imaging (EMSI) • Imaging FT-IR spectroscopy

4. Pattern formation on catalysts J. Lauterbach, et al., Surface Science 294 (1993) 116

5. Ellipsomicroscopy for Surface Imaging (EMSI)

6. P > 10-3 mbar -> EMSI T = 540 K, CO/O2 = 0.11. Image size:1mm x 1.25 mm, dt = 0.33 s Video Lele, T. and J. Lauterbach, Chaos12(1) (2002) 164-171.

7. TiO2 surface structure - LEEM Sample -20 keV Photons (uv, x-rays) 777°C 761°C 0.5 m Electron emitter Image 755°C 755°C Dark field Low Energy Electron Microscopy & Synchrotron-based Photoemission Electron Microscopy RuO2 growth

8. Probing of Valence Electrons with X-rays Atom specific Orbital symmetry selective Experiment--Theory

9. Catalytic Chemistry with Orbitals Haber-Bosch N2 + 3H2 2NH3 Hansen et.al. Science 294, 1508 (2001) New Ru Catalyst Active site at steps Probe pulse at different delay time Dt Theoretical simulations, Mats Nyberg, Stockholm University Both N atoms

10. XASpectroelectrochemistry • Element specific • Resolves multiple redox sites • Perfect for fuel cells

11. New Tools for Neutron Scattering: • Parallel detectors offer more sensitivity • Vibrational spectroscopy without selection rules Determination ofChloroform Adsorption site in Faujasite From H pair distribution function. (J. Eckert, C. Mellot-Draznieks and A. K. Cheetham, J. Am. Chem. Soc. 2002, 124, 170 )

12. AFM image of polyethylene formed by a single catalytic site: Cr on SiO2 / Si(100) Paraboloid: Height h0 = 3.1 nm ± 0.1 nm radius r0 = 24 nm +2 nm(tip) Volume V = pi/2 h0 r02 = 2800 nm3 density [PE] = 25 molecules/nm3 AFM image 100 x 100 nm heigth 3 nm TOF = 19 ± 2 molecules / s Peter Thüne, Joachim Loos, Piet Lemstra, Hans Niemantsverdriet, Macromol Symposia 2001

13. Atomic Resolution Images Under High Pressure Conditions 1 bar H2 (during) 10-13 bar (before) 10-9 bar (after) Pressure-induced reconstructions on Cu(110) exposed to H2 Laegsgaard, Osterlund, Thostrup, Rasmussen, Stensgaard and Besenbacher , Rev. Sci. Instrum. 72 (2001), 3537-3542. In-situ HRTEM offers defect analysis - identification of active sites in vanadyl pyrophosphate catalysts

14. Z-contrast STEM Z=33 Z=31 As Ga 1.4Å EELS

15. EELS profile across a single particle Co L2,3-edges Ni L2,3-edges Intensity (a.u.) Energy Loss (eV) 760 800 840 880 100 Co Ni 80 60 40 20 0 1 2 3 4 5 6 7 2nm Co/Ni Concentration profile

16. [001] [110] Imaging of Active Catalyst Atom Configurations g g Pt on -alumina Pt on -alumina 0.5 Å probe 1.3 Å probe Pt atoms sit in surface vacancies