Thermal Energy Ion-Molecule Reactions

Abstract

Publisher Summary This chapter describes various aspects of thermal energy ion-molecule reactions. Some new experimental techniques have led to a great deal of quantitative information on ion-molecule reactions, especially for reactions involving small molecules at low energies. The majority of ion-molecule reaction rates has been measured in experiments utilizing the ion source of a mass spectrometer. A product ion may be produced from several reactions and the separation into the component reactions is often uncertain. The ability to vary the ion energy can be used to advantage in mass spectrometer ion sources, as the energy dependence of reactions can be investigated in this way. A few endothermic reactions have been studied in mass spectrometer ion sources, with the accelerating field supplying sufficient kinetic energy to make the reaction observable. The atomic positive ions are produced in weak plasma and largely deexcited to the ground state by superelastic collisions with electrons before reaching the neutral port. The ion-atom interchange reaction is also elaborated in this chapter.