Cross-section study of ion-molecule reactions of planetary importance

Using the unique triple-quadrupole double-octopole (TQDO) photoionization and electron-impact apparatus developed in our laboratory, the absolute state-selected cross sections for the ion-molecule reactions involving O+(4S,2D,2P) and many other neutral molecules of importance in the ionosphere are measured over a collision energy range from near thermal energy to above 10eV. Good agreement with other people\u27s results are found. A simple method to isolate O+(2D) and O+(2P) is developed. Because of the nature of the TQDO apparatus, the kinetic energy spread of the prepared ions is around 1eV, which is not good enough for the study of low-energy ion-molecule collision processes. A differential retarding potential method is developed for improving the kinetic energy resolution. With this method, the cross sections for reactions with collision energy below 0.1eV can be studied. Modern computer-based instrumentation technology is applied to the TQDO system for improved efficiency and more reliable data-acquisition processes