Tandem Flowing Afterglow-Selected Ion Flow Tube and Its Application to the Thermal Energy Reaction of (sup 18)O(sup -)

摘要

Since its development by Ferguson, Fehsenfeld, and Schmeltekopf in 1963, the flowing afterglow (FA) has proven to be a valuable technique for studying the kinetics, thermochemistry, and detailed dynamics of gas-phase ion-molecule reactions. The capabilities of this method were greatly extended by Adams and Smith in 1976 by their development of the selected ion flow tube (SIFT); in the last decade several research groups have applied this technique to a variety of important chemical problems. We wish to report the design and construction of a tandem FA-SIFT instrument with considerably enhanced sensitivity, resolution, and chemical versatility. With this instrument we have generated oxygen 18(-) from isotopically unenriched precursors and studied its chemistry with a variety of reagents. These studies provide the first thermal energy rate constants for these processes and reveal several previously hidden reactions; in particular, it is found that isotope exchange competes with associative detachment in the reactions of oxygen(-) with carbon monoxide and sulfur dioxide.