|Physical & Theoretical|
The properties of the interfaces between two phases play an important role in many physical and chemical processes - catalysis, adhesion, corrosion, friction, etc. Increasingly refined spectroscopic tools are being developed and used to study interfaces. At McMaster we place particular emphasis on studies of the gas-solid interface using ultra-high vacuum techniques. This includes investigation of the surface properties of pure metals and alloys with relevance to heterogeneous catalysis. A large effort is also directed at developing new surface analysis techniques based on inner-shell electronic excitation by electron and X-ray impact. These techniques are then applied to study a variety of interfaces ranging from reactions of organic species at metal surfaces to the composition and structure of buried semiconductor interfaces.
Energy levels of molecules, ranging from the microwave domain of electron and nuclear spins (ESR, NMR), through the regimes of vibrational modes (IR, Raman), valence electronic processes (vis-UV), on to inner-shell processes (X-ray absorption) and even up to nuclear excitation (Mössbauer) are all studied at McMaster. Conventional and laser optical techniques as well as synchrotron radiation and charged particle impact spectroscopies are being used for analysis. As physical chemists we are interested in studying molecular structure and internal molecular motion by NMR, the creation and decay of highly excited inner-shell states through electron energy loss and synchrotron X-ray absorption techniques, and the short time scale dynamics of intra- and inter-molecular interactions via sub-picosecond laser techniques.
A Good theory should both interpret experimental results within existing scientific frameworks, and provide predictions which may expose the limitations of just these frameworks. This is true for the atomic domain of quantum mechanics, for the interface of quantum and classical descriptions called statistical mechanics, and for macroscopic effects and reactions treated by thermodynamics and kinetics. One of our groups has developed improved quantum mechanical interpretations of the electronic charge distributions in molecules, thereby clarifying the nature of chemical bonding. Others combine quantum mechanics with experiments to correlate molecular structures with intramolecular motion and tunnelling processes. Statistical theories of kinetics and dynamics in both the "smooth" and chaotic regimes are under study as well.