The Interior of Single Molecules

Monday, 25. Februay, 8:30 h, H 0105

Spatially resolved inelastic electron tunneling with a low temperature scanning tunneling microscope (STM) has led to new understanding into a broad spectrum of molecular properties, including particularly, the revelation of variations in the coupling of different parts of a single molecule to external particles, such as electrons and photons. Examples of such spatially resolved inelastic tunneling are vibrational excitation, vibronic spectroscopy, vibrationally resolved fluorescence, and light driven phenomena. The STM makes it possible to inject or remove an electron from a specific point r₀ of the molecule at t=0, i.e. setting up an initial, nonstationary state Φ(r₀,0), and measure the influence of the chosen r₀ on the molecule’s properties. Such experiments lead to spatial control of the properties and functions of molecules in isolation and in aggregates, as well as providing direct visualization of nanoscale phenomena and removing ensemble averaging in the measurement. It is now possible to study the interior of single molecules in real space, and literally visualize their inner machineries in various processes such as energy transfer, conformational changes, diffusion, electron transport, bond formation and dissociation, electron transfer, chemical sensing, and responses of the molecule to light. These studies provide the link between the interior excitations and motions with the macroscopic molecular properties.

Wilson Ho
Department of Physics, University of California, Irvine, CA 92697-4575, USA