My major research project involves the spectroscopic and theoretical investigation of transient intermediates and weak molecular complexes. The identities and geometric structures of these transient intermediates are elucidated primarily by performing matrix-isolation infrared spectroscopy experiments. Matrix-isolation is a technique by which normally unstable species (often radicals) are trapped in a frozen matrix of inert gas (generally argon) near 10 degrees Kelvin. The extremely low temperature reduces the possibility of unimolecular decomposition of the trapped species and the matrix of inert gas prevents bimolecular or aggregation reactions between trapped species. Once trapped in the low temperature, noble gas matrix, the infrared spectra of the trapped species can be examined. In order to trap and study unstable molecules, they need to be generated in sufficient quantities in the gas phase first. This is often accomplished by decomposing a stable molecule or molecules into the desired fragment species using some type of energy source, for example, light, heat, electrical energy, etc. In my lab we will primarily use microwave discharge, pyrolysis, and photolysis as the sources to generate the desired intermediates. Spectral assignments and geometric structure determinations of the trapped species will be established by performing experiments with isotopically substituted reagents, matrix annealing experiments (warming and re-freezing the matrix), matrix photolysis experiments, and by theoretical quantum mechanical calculations (ab initio and density functional theory) using the Gaussian suite of programs. Two projects ongoing in my laboratory are concerned with the investigation of the nitrogen containing transient intermediates related to: (1) silicon nitride (Si3N4) chemical vapor deposition processes using silane (SiH4) and ammonia (NH3) or silane and nitrogen (N2) mixtures and (2) titanium nitride (TiN) chemical vapor deposition processes using titanium tetrachloride (TiCl4) and NH3 or TiCl4 and N2 mixtures. Another project we are working on is the characterization of weakly bound lone pair-pi complexes, such as H2O-C6F6. A student who works with me on these projects will learn high vacuum techniques, gas handling techniques, Fourier- transform infrared spectroscopy and instrumentation, theoretical quantum mechanical calculations (Gaussian program), and the approach to good scientific inquiry.
