Method for Studying Low Energy Ion-Molecule Reactions Using Monoenergetic Ions

Abstract

An experimental technique is described for the study of ion-molecule reactions permitting the investigation of ions with kinetic energies in the range 0–3 eV which introduces negligible spread in ion energy. A 20 nsec ionizing pulse is used to produce ions in the reaction chamber to which a steady dc electric field is applied. Because of the short time interval for ionization all ions have essentially the same energy and move as a ``bunch'' under the influence of the applied field. Thus the energy of the ions at any subsequent time may be readily calculated, and the energy dependence of ion-molecular interactions may be studied. Practical considerations, determined by source dimensions, limited the maximum energy to 1.3 eV in the present study for the reaction CH4++CH4 → CH5++CH3.