Starts 27 May 2009 17:00
Ends 27 May 2009 20:00
Central European Time
Leonardo da Vinci Building Seminar Room
Strada Costiera, 11 I - 34151 Trieste (Italy)
Solids are characterized by their different degrees of freedom charge, lattice, and spin. Coupling of these degrees of freedom to each other results in fundamental phenomena like superconductivity (electron-phonon coupling) or the Kondo effect (spin-dependent electron scattering). Time-resolved spectroscopy employing femtosecond laser pulses faciliates direct and independent access of these degrees of freedom and occasionally novel insight into coupling mechanisms. In this talk two examples will be presented. (a) Quasi-one dimensional structurs form charge density waves. Using time- and angle-resolved photoelectron spectroscopy we have succeeded to monitor the single and many particle excitations in the charge density wave compound TbTe_3 close to thermodynamic equilibrium. In case of more intense optical excitation non-equilibrium conditions are generated, which finally lead to melting of the charge density wave and facilitate an identification of the responsible mode. (b) Electron injection from a metal substrate into ice layers results in localization and subsequent stabilization of these excess electrons, which occurs by electron-induced rearrangement of water molecules. Due to the permanent electrical dipole moment this process is refered to as electron solvation and we find a pronounced correlation of ice structure and solvation dynamics at such ice-metal interfaces. Electron traps at crystalline ice surfaces, which exhibit extremely long hot electron lifetimes up to minutes, present a model system for specfic reaction sites as demonstrated for electron induced dissociation of Freon adsorbed on ice.
  • M. Poropat