Detailed Studies of Cold and Ultracold Ions in RF Traps

The physics and chemistry determining the composition of the interstellar medium is quite different from other chemical systems since low densities ($<$~10$^{7}$~cm$^{{\-}3})$ and low temperatures prevail. For example, modeling the early stages of protostellar collapse requires a detailed understanding of ultracold hydrogen plasmas. This contribution concentrates on recent results in the field of cold gas phase ion chemistry, producing, modifying or destroying C$_{m}$H$_{n}^{+}$ ions and their deuterated variants (m$\ge $0, n$\ge $0). All experimental activities with charged particles are based on \textit{inhomogeneous, time dependent electric fields}, created with suitable electrode arrangements. Rather complex machines have been constructed by combining for example temperature variable multi-electrode ion traps (e.g. a 22-pole trap) with atomic or molecular beams. In addition analytical tools such as laser induced reactions are used in order to understand the low energy dynamics on a state specific level. It is emphasized that reactions (in the trap or in space) often do not reach thermodynamical equilibrium, especially if traces of ortho-hydrogen are present.