High-res infrared studies of molecular clusters, ethane, chemical intermediates and hydrocarbons

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The focus of this proposal is two-fold. First is experimental investigation of van der Waals (vdW) forces between neutral molecules. vdW forces are many orders of magnitude weaker than chemical bonds. However, they act over a much longer range and as a result they play an important role in formation of molecular clusters, liquids and solids. ***The evolution from gas phase to bulk can be traced by probing the properties of clusters. A cluster is an aggregate of bound atoms or molecules. Some clusters have size-dependent physicochemical properties which are different from those of the bulk. Others such as clusters of CO2 are of great interest in atmospheric and industrial chemistry. For example, under supercritical conditions CO2 is used a benign industrial solvent.***These intermolecular forces can be directly probed by means of high-resolution spectroscopy, an experimental technique which we intend to use. We will investigate clusters with the aim of answering basic questions such as “how do differing structures of a given cluster size influence the growth of larger ones?” and “does the system has preferred pathways?” These questions are relevant in atmospheric chemistry, biomedical, electronics, and materials science. Our experimental results also provide a challenge to quantum chemical calculations of weak forces, which thereby helps to advance the state of the theory. The theory in turn can be used for calculations on large systems of biological significance, like protein folding. ***The second objective is to analyse laboratory based spectra of ethane to provide data for compilation on databases recognized as international standards. We will provide quantum mechanical models for frequency and intensity of ethane bands in the mid infrared region. Here, the challenge lies in understanding the basic physical questions relating to the role that large amplitude twisting of CH3 groups play in coupling the other vibrational modes. The interest in resolving such basic physical questions relates to the fact that CH3 groups are present in many larger bio-molecules and it is the motion of these groups that determine the dynamical properties and functions of these systems. The end users of our laboratory data are scientists with interest in terrestrial and planetary atmospheric remote sensing, transmission simulations, industrial process monitoring, and pollution regulatory studies.***Although the research we propose is fundamental in nature it has important consequences in fields with practical importance. The most obvious way in which Canada will benefit from the proposed projects is via the training of students and postdoctoral fellows. In Canada and elsewhere computational, optical, material sciences are used to guide the discovery of new drugs, study global warming, predict weather patterns etc. Maintaining the pace of growth and Canada's technological prowess require well trained scientists.