Association reactions. Theoretical shortcomings

Abstract

Measurements of the rate coefficients of four ternary ion–molecule association reactions have been performed with a SIFT (selected ion flow tube) apparatus in the temperature range 80–480 K. Theoretical values for the rate coefficients have been presented in the literature or are calculated here. For only one reaction are theoretical and experimental rate coefficients in reasonable agreement. Possible reasons for the theoretical shortcomings are discussed and it is concluded that the existence of several isomeric forms of the product ions can make theoretical treatments ineffective unless ab initio quantum-chemical calculations are available to indicate which isomers can be readily formed from reactants.