Theoretical Aspects of Chemical Dynamics: Ion-Molecule Collisions, Energy-Time Analysis of Molecular Spectra, and Assignment of Quantum States

点击翻译按钮获取中文摘要

Professor Ezra of Cornell University is being supported by the Theoretical and Computational Chemistry program to continue his work on the theoretical investigation of chemical dynamics. Specifically the project is a computational study whereby complex high lying vibrational states are investigated by quantum, classical and semiclassical methods. During this next grant period he will investigate the dynamics of ion-molecule collisions, with particular emphasis on the formation and decay of long lived collision complexes. This research will also focus on the development of semiclassical periodic orbit theory as an aid in the interpretation of molecular vibrational spectra which are of sufficiently high energy that they lie beyond the regime of traditional spectroscopic techniques. These topic address several fundamental problems in chemical and molecular physics namely the fate of energy distribution of long lived molecular complexes and statistical versus non-statistical behavior in the unimolecular decay of transient species. During the following two years Prof. Ezra will be concerned with the theoretical analysis of the internal motions in molecules, as they vibrate, rotate, and collide with one another. The study of these patterns of nuclear motion leads to a deeper understanding of the factors that determine the propensity of molecules to undergo reaction under given conditions. This research group will be studying a number of topics relevant to this general theme. First, they will investigate the nature of the ``sticky'' collisions that can occur between charged species and uncharged molecules in, for example, reactions of atmospheric importance. Such sticky collisions are often essential for subsequent chemical reaction to occur. Another major topic is the development of methods that enable the nature of nuclear motions within molecules to be inferred in a fairly direct way from molecular vibrational spectra. Much of this work exploits semiclassical ideas: that is, theories that are correct with respect to quantum mechanics, while retaining the intuitive appeal of classical ball-and-spring pictures of nuclear motion. Periodic classical motions of nuclei, those that repeat over and over ad infinitum, are found to play an important role in understanding the connection between spectra and nuclear dynamics.