COLL 181 |
| Inelastic electron process that leads to vibrational excitation has attracted much attention. Considering that the conduction electrons passes through the electronic state crossing the Fermi level or hopping through the HOMO or LUMO state of the molecule, the electronic state that appears close to the Fermi level of the electrode should play a crucial role in the elemental process. The inelastic tunneling process of electrons between the tip of an STM and the target molecule at metal surfaces lead to various dynamical motion of molecules at surfaces, such as desorption, lateral hopping, rotation and chemical reaction via the excitation of vibrational modes of adsorbed molecules. The vibrational modes that are excited through the process could be defined through the response of the molecular motion to the applied bias voltage, i.e. action spectrum. Action spectra for hopping motion of cis-2-butene on Pd(110), cleavage of dimethl-disulfide on Cu(111) and hopping motion of cleaved product methyl-thiol show clear thresholds in bias voltage that are equivalent to certain vibration modes, the excitation mechanism of which can be understood by the resonant tunneling mechanism. When the electron jumps into or out of a certain molecular orbital, molecules will temporally go through the negative or positive ion state, where vibration states can be excited, during the relaxation process. |
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Dynamics of Single Atoms, Molecules and Clusters on Surfaces
2:00 PM-5:30 PM, Monday, 11 September 2006 Sir Francis Drake -- Renaissance Room, Oral
Division of Colloid & Surface Chemistry |