Chemistry at the Spatial Limit

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The aim of this research is to obtain detailed descriptions of single atoms and molecules. These experiments provide the basis for understanding chemical and physical processes at surfaces and properties of nanostructured condensed matter and molecular materials. Low temperature scanning tunneling microscopes (STM) are used to image, manipulate, chemically modify, and spectroscopically identify individual atoms and molecules. The development of the single molecule vibrational probe by inelastic electron tunneling spectroscopy (STM-IETS) provides a new analytical technique with unprecedented spatial resolution. It is now possible to investigate chemistry at the spatial limit with the STM; the results provide a view of chemistry not possible by studying an ensemble of molecules. In particular, the fundamental motions in molecules (vibration, rotation, translation), the coupling of tunneling electrons to nuclear motions (charge and energy transfers), and electrical conductivity (as related to molecular electronics) can be studied with single molecule sensitivity. The tunnel junction forms a novel nanoreactor in which the tip and the substrate can be used together to carry out unimolecular dissociation and bimolecular reactions. The research covers selected chemical systems from the lightest element (hydrogen atoms) to diatomic (carbon monoxide) and larger organic molecules (thios) on metal surfaces. These studies will lead to the development of a method to detect single electron spins in individual atoms and molecules by the STM. A thin film of magnetic metal (iron, gadolinium) is evaporated on the STM tip to provide a source of spin polarized electrons. The study of single and small aggregates of Manganese, Cobalt, Nickel, and Iron atoms, nitric oxide and nitric oxide dimers, 1,1-diphenyl-2-picryl-hydrazyl (DPPH), and other molecules with unpaired spins provides a new way to understand magnetism at the atomic scale and illuminates the role of the electron spins in chemistry. Overall, these experiments are intended to illuminate general experimental procedures and scientific understandings. The research on solid surfaces is fundamental in nature and provides a foundation for a broader understanding of chemistry in the gas phase, solution, and other condensed media.%%%An integral part of the proposed research involves the scientific training and development of undergraduate and graduate students. Since the STMs (microscope, electronics, and software) are homemade, the students have a unique opportunity to be involved in the design and construction of new generations of STMs. In addition, UC Irvine has established centers to reach out to local K-12 schools which have large populations of underrepresented groups. The P.I. will teach a special topics course on "Nanoscience" which will attract an interdisciplinary group of students from physics, chemistry, biology, and engineering. While the emphasis of the proposed research is to obtain a fundamental understanding, the implications for futuristic technologies are apparent, and students trained in these areas will be highly competitive in the job market. This project is being co-funded by the Chemistry Division/Analytical and Surface Chemistry Program and the Division of Materials Research/Solid State Chemistry Program.