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DIET: Changes and constants in changing times.

DIET: Changes and constants in changing times. Dietrich Menzel Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin and Physik-Dept. E20, Techn. Univ. München, Garching (Germany). In memoriam Ted Madey Distinguished scientist longtime Close friend frequent collaborator. Early times:

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DIET: Changes and constants in changing times.

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  1. DIET: Changes and constants in changing times. Dietrich Menzel Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin and Physik-Dept. E20, Techn. Univ. München, Garching (Germany)

  2. In memoriam Ted MadeyDistinguished scientistlongtimeClose friend frequent collaborator

  3. Early times: 1963 1973/74

  4. Gomerfest May 1996

  5. Excited state chemistry: Reactivity induced by electronically excited states Steep potential in F.C.- region couples electronic to nuclear oordinates Curve crossings can lead to nonadiabatic behavior • Adsorbates at surfaces: Coupling/bonding to surface induces changes in molecules which change reactivity in thermally accessible states (catalysis, electrochemistry, layer growth etc.) RAB

  6. EID, ESD, DIET, • Surface photochemistry: • Coupling to surface also changes excited states and introduces possible charge and energy transfer: • ÞPhotochemistry changed Concentrate on first step: Breaking of bonds (dissociation, desorption)

  7. Changes:MethodsMachines and radiation sources

  8. The heroic times : 1962-1964 Paul Redhead, Can. J. Phys. 42, 886 (1964)

  9. Today‘s uhv machinery: 10 cm 3 m

  10. Today‘s radiation sources: Behemoths 1 cm 5 m (lasers); 100 m (SR sources)

  11. Constants in understanding: Principles, mechanisms, and counteracting influences

  12. DIET mechanisms - Energy Energy Energy Z Z Z Adsorbate or substrate mediated, depending on location of primary excitation Direct Hot electron -TNI DIMET Localization vs. delocalization; steepness of potential

  13. Adsorbates on metal and semiconductor surfaces • Observations: • (For excitations by electrons or photons) • Compared to corresponding molecular processes: • Considerably more neutrals than ions(except high exc.) • Strong decreasesof cross sections, which are very sensitive to • bonding mode • type of primary excitation (valence-double valence-core- core satellite) • adsorbate density and order • defects • mass(isotope effect !!)

  14. Adsorbates on metal and semiconductor surfaces • Observations: • (For excitations by electrons or photons) • Compared to corresponding molecular processes: • Considerably more neutrals than ions(except high exc.) • Strong decreasesof cross sections, which are very sensitive to • bonding mode • type of primary excitation (valence-double valence-core- core satellite) • adsorbate density and order • defects • mass(isotope effect !!) Explanation: Competition between bond dissociationand transfer of excitation (quenching by energy and/or charge transfer): LOCALISATION vs. DELOCALISATION must be VERY fast !

  15. Direct observation of ultrafast CT processes:Laser pump-probe, and Core hole clock See, e.g., D. Menzel, Chem.Soc. Rev. 37, 2212, 2008, and cited work

  16. Some early successes: Isotope effect ESDIAD Strongly localising excitations (core, complex)

  17. Some early successes: Isotope effect ESDIAD Strongly localising excitations (core, complex) But not only DIET: The ruthenium story: TPD, LEED, Auger, DF CO (T.E.M.+D.M., Japan J. Appl. Phys. Suppl. 2 (1974) 229) O2 and CO oxid. (T.E.M., HA Engelhardt, D.M., SS 48(1975) 304) XPS: Valence bands, Satellites, CO and O w. John Fuggle, M. Steinkilberg(Phys. Lett. 51A (1975) 163; CPL 33 (1975) 233; SS 52 (1975) 521)

  18. Some recent examples: Alkalis on the moon: “Far-out surface science“ B. Yakshinsky and T.E. Madey, Nature 400 (1999) 642

  19. Some recent examples: Alkalis on the moon: “Far-out surface science“ Yakshinsky and Madey, Nature 400 (1999) 642 Water on Ru(0001): Extreme radiation sensitivity N.S. Faradzhev, K.L. Kostov, P. Feulner, T.E. Madey, and D. Menzel, Chem. Phys. Letters 415 (2005) 165: “Stability of water monolayers on Ru(0001): Thermal and electronically induced dissociation”

  20. Some recent examples: Alkalis on the moon: “Far-out surface science“ Yakshinsky and Madey, Nature 400 (1999) 642 Water on Ru(0001): Faradzhev, Kostov, Feulner, Madey, Menzel, CPL 415 (2005) 165 Insensitivity of large conjugated p-systems to radiation damage: D. Menzel, P. Cloutier, L. Sanche, T.E. Madey, J. Phys. Chem. A 111 (2007) 12427: “Low-energy electron-induced damage in fluorinated copper phthalocyanine films, observed by F- desorption: Why so little damage ?” “The capacity of DNA to resist photodamage by rapidly dissipating the energy from ultraviolet light absorption is a key feature of long-term genetic stability. Many model studies have probed the underlying dynamics responsible for this dissipation, (Science 322, Oct.10,2008)“

  21. Some recent examples: Alkalis on the moon: “Far-out surface science“ Yakshinsky and Madey, Nature 400 (1999) 642 Water on Ru(0001): Faradzhev, Kostov, Feulner, Madey, Menzel, Chem. Phys. Letters 415 (2005) 165 Insensitivity of large conjugated p-systems to radiation damage: Menzel, Cloutier, Sanche, Madey, J. Phys. Chem. A 111 (2007) 12427 Nanostructures (facetted surfaces as structural selfassembly): T. E. Madey, W. Chen, H. Wang, P. Kaghazchi, T. Jacob, Chem. Soc. Rev. 37 (2008) 2310 DIET on metal nanoparticles: K. Watanabe, D. Menzel, N. Nilius, H.-J. Freund, in Photochemistry and Photophysics on Surfaces,Ed. J.T.Yates, Jr., Chem. Reviews 106 (2006) 4301; PRL 99(2007)225501 and 101 (2008) 146103.

  22. Thank you !

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