19 Davey Lab
Penn State UniversityContacts:
Paul S. Weiss: stm@psu.edu
Charlie Sykes: ech@stm1.chem.psu.edu
Patrick Han: pxh164@psu.edu
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We use a Low Temperature-Ultra High Vacuum (LT-UHV) STM to study molecular adsorbates on surfaces. The high stability of the microscope at low temperatures (4 K) allows us to take data over individual molecules on a timescale of days. Systems of interest are currently weakly physisorbed molecules (CS2, C2N2, C6H6 and C6D6) on the Au{111}surface. We have assigned incommersurate overlayer structures and explained structure in terms of intermolecular quadrupolar interactions. We are interested in how the standing waves created by scattering of surface state electrons from step edges and point defects effect molecular adsorption. Our results to date demonstrate that the electrophilic/nucleophic nature of the adsorbate determines its adsorption site; electrophilic CS2 interacts most strongly with the electron rich crests of the standing waves originating from electrons at the Fermi energy. Currently we are recording Inelastic Electron Tunneling Spectra (IETS) over single molecules and hope to demonstrate an adsorption site dependancy in each molecule's vibrational spectra.
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