Vibrational excitation of polyatomic molecules by electron- and positron-collisions

Abstract

Electron-impact vibrational excitation is an important elementary process in a molecular plasma in space (e.g., ionospheres of Earth and other planets) and laboratory (e.g., plasma processing).1 It is also important in the radiation interactions with matter. Vibrational excitation is the most dominant energy-loss process of low-energy electrons (say, below tens of eV). Furthermore, once excited vibrationally, molecules are very active in collisions with other particles. For example, the dissociative attachment cross section is by many orders of magnitudes larger for a vibrationally excited molecule than for a ground-state one. Thus the electron-impact vibrational excitation has been extensively studied for long time. Because of their simplicity, however, most of the theoretical studies so far are mainly concerned with diatomic molecules. The present author has developed a theoretical method to treat polyatomic molecules in a correct manner.1 Based on the result of the calculations using the method, one aspect of the vibrational excitation of polyatomic molecules is discussed here.