Local vibronic and geometric structure of large organic adsorbates: New experimental approaches to chemisorption by STM-IETS and NIXSW

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In this project we are going to investigate the chemical bond between metal surfaces and complex p-conjugated organic adsorbates. We focus on the internal vibronic and geometric structure of the adsorbate as a key to an improved understanding of the chemisorption bond. Two experimental techniques which have so far not been fully exploited in this field, namely STM-based inelastic tunnelling spectroscopy (IETS) and normal incidence X-ray standing wave techniques (NIXSW), will be applied. Between them, they should allow (i) improved (spectroscopic) inplane imaging of complex molecular entities, (ii) element-specific determination of structural bond parameters with high precision, and (iii) spectroscopic characterisation of the chemisorption bond at the level of single molecules and below, enabling e.g. the molecule-by-molecule distinction of coexisting chemisorption states and mode-selective switching between them. Results of these experiments will be compared to ab-initio density functional calculations of the combined adsorbatesubstrate system. The chosen approach will aid the development of chemisorption models that take the extended nature, flexibility and multifunctionality of organic adsorbates into account. Finally, the influence of artificially created nanostructures on chemisorption properties of organic adsorbates will be explored.