Conclusions
Ion-molecule association reactions and the corresponding reactions of neutral species have much in common and, therefore, should be interpreted and modeled by the same theoretical framework. Nevertheless, there are also characteristic differences which require specific changes of the analysis. On the energy transfer side, different collision frequencies Z have to be considered while average energies 〈Δ E 〉 appear to be of similar size in ionic and related neutral systems. Specific rigidity factors f rigid (E,J) and centrifugal barriers E 0 (E,J) may also be characteristically different, but such differences have only minor influences on reduced falloff curves. Finally, capture rate constants determining the high pressure rate coefficients in ionic systems are governed by long range electrostatic potentials in a way which can well be expressed by the analytical representation of classical trajectory results.