Gas-Phase Electron Diffraction Applied to Molecules Undergoing Large-Amplitude Motion

Abstract

A review with 23 refs. on the development of gas-phase electron diffraction as a tool for the investigation of mol. vibration. The methods used for \"stiff\" mols., methods based on harmonic vibration theory, are not adequate for the description of large-amplitude motion. In such cases the motion is represented by a set of \"pseudoconformers\", constructions representing the instantaneous conformations of the mol. in question, each pseudoconformer representative of a finite displacement of the large-amplitude coordinate. These pseudoconformers are treated as normal mols. undergoing harmonic vibrations of their frames exclusive of vibration along the large-amplitude coordinate. Each is given a wt. detd. by a Boltzmann distribution in which the potential for the large-amplitude motion appears as the energy factor. The method is applicable to all types of large-amplitude motion. It is illustrated by several examples of internal rotation and several forms of the potential. [on SciFinder (R)]