Fundamentals of ion–molecule chemistry

Abstract

The dependence of ion–molecule reactions on kinetic and internal energy is explored from both experimental and theoretical points of view. The conversion of raw data (ion intensities versus laboratory energies) to instrument independent information (reaction cross sections versus center-of-mass energies) is explained in detail. The characteristic experimental behavior of ion–molecule reactions as a function of kinetic energy is illustrated and then theoretically characterized. The conversion and relationship between reaction cross sections and rate constants is provided along with examples. The changes in reaction efficiencies with changes in internal excitation are examined, with appropriate examples. Various explanations for why exothermic ion–molecule reactions are not always efficient are then provided along with several illustrative experimental cases. The factors that influence the efficiency of dissociative processes are also elucidated. The relevance of these various considerations for application to atomic mass spectrometry is explored throughout.