Invited Paper SS-TuM1
Gaede Langmuir Award Lecture: Probing Elementary Process in Chemical Dynamics at Surfaces

Tuesday, October 21, 2008, 8:00 am, Room 208

Chemical reactions and energy transfer processes at the gas-surface interface play a vital role in a wide range of scientific and technological problems. In the electronics industries etching and deposition are key steps in the fabrication of microelectronic components. Heterogeneous catalysis lies at the heart of many synthetic cycles in the chemical and pharmaceutical industries. Gas-surface reactions also play an important role in the environment, from acid rain to the ozone hole. Energy transfer at the gas-surface interface influences flight, controlling spacecraft drag, and the altitude of a slider above a computer hard disk. Often such processes involve a complex sequence of events. To develop a molecular level understanding we must find ways to isolate and separately study the elementary processes involved at each step. Molecular beam and laser techniques provide a remarkably rich set of tools to accomplish this decomposition into elementary steps. The method is conceptually very simple. We prepare beams of molecules with well defined properties and scatter these beams for well defined surfaces under UHV conditions. It is possible to control the chemical composition, angle of incidence, kinetic energy, electronic state, vibrational state, rotational state, and even the molecular orientation of the impinging molecules. We then make time resolved observations of the changes in these variables after interaction the surface. The observations provide signatures of the elementary dynamical processes that contribute to a given overall process. They also provide quantitative measures of the rates and cross sections involved and thus provide benchmarks for the development of theory.