Isotope effects in the bimolecular reactions of gaseous ions. Concepts, techniques, and reactions

Abstract

AbstractFoundations of isotope effects are examined in terms of concepts, models, and theories. Leading instrumental methods for bimoleculur reactions are reviewed: the guided ion beum mass spectrometer (GIBMS) and the selected ion flow tube (SIFT). In their most elaborate forms, both methods can select the translational energies of the reacting ions and the temperatures of the neutral molecules. This capability gives extraordinary control over bimolecular ion/molecule reactions. Experiments on simple systems can sometimes identify the effects of particular forms of internal energy. Isotope effects appear in numerous reaction types and behave in several ways as functions of ion translational energy and temperature. For endothermic reactions, they can become very large at low temperatures, a matter of much interest in astrophysics. © 1996 John Wiley & Sons, Inc.