In this project in the Physical Chemistry Program of the Chemistry Division, Professor Lee H. Spangler of Montana State University will study the effect of the electronic state of a molecule on interactions between its non-rigid parts. Specifically, methyl and amine interactions will be examined as a function of distance in molecules with pi-electron systems using various spectroscopic techniques applied to samples prepared in a supersonic jet expansion. An understanding of the influence of electronic state on conformational changes is expected to result. %%% The large amplitude, low frequency motions of molecules affect the conformational preferences and reaction specificity of those molecules. For example, knowledge of the conformation of a reagent molecule obtained from the fundamental study of the structure of a much smaller related species allowed one researcher to devise a synthetic route for a large class of polyether antibiotics. A detailed understanding of what determines conformational preferences as a function of molecular environment and electronic state is also key to understanding biological activity. The current project aims at gathering conformational information in several types of molecular systems.