Chemistry with Controlled Ions

This chapter focuses on the application of controlled-molecule techniques for precise studies of ion-molecule reactions in the gas phase. It gives an overview of the most important techniques presently used for the control of the translational motion, internal quantum states, and structural properties of molecular ions and neutral molecules in the gas phase. Besides the control of the translational motion, preparation of the internal quantum state of molecular ions is a main prerequisite on the way to controlling chemical reactions. Since the 1980s, (multiphoton) photoionization has been a key method for preparing molecular ions in selected internal states. Various variants of this approach have been implemented. The chapter further gives a brief outline of salient concepts of ion-molecule reaction dynamics which are relevant for the present discussion. Finally, the chapter presents some illustrative examples in which cold- and controlled-molecule techniques have been used to study the mechanisms and dynamics of ionic reactions.