Ion-molecule kinetics

As with most methods for studying ion-molecule kinetics and dynamics, numerous variations exist. For low-energy processes, the collision cell can be replaced with a molecular beam perpendicular to the ion beam [106]. This greatly reduces the thennal energy spread of the reactant neutral. Another approach for low energies is to use a merged beam [103]. In this system the supersonic expansion is aimed at the tluoat of the octopole, and the ions are passed tluough... 

A radical solution to all of the above-mentioned difficulties is to eliminate the solvent medium entirely and to measure structural effects on heteroaromatic reactivity in the gas phase. During the last decade, a revolution has occurred in the experimental and theoretical approaches to understanding gas-phase ion chemistry. This has occurred as the result of the simultaneous development of several experimental methods for studying organic ion-molecule kinetics and equilibria in the gas phase with precision and range of effects equivalent to or even better than that normally obtained in solution and by very sophisticated molecular orbital calculations. The importance of reactivity studies in the gas phase is twofold. Direct comparison of rates and equilibria in gaseous and condensed media reveals previously inaccessible effects of ion solvation. In addition, reactivity data in the gas phase provide a direct evaluation of the fundamental, intrinsic properties of molecules and represent a unique yardstick against which the validity of theoretical estimates of such properties can be adequately assayed. 

The vast majority of the work on ion-molecule kinetics has been performed at room temperature. A fraction of these room temperature kinetic studies have been made as a function of ion translational energy. However, temperature dependent studies have been limited mostly to... 

ION-MOLECULE KINETICS AT HIGH TEMPERATURES (300-1800 K) DERIVATION OE INTERNAL ENERGY DEPENDENCIES A. A. Viggiano and Skip Williams 85... 

As with most methods for studying ion-molecule kinetics and dynamics, numerous variations exist. For low-energy processes, the collision cell can be replaced with a molecular beam perpendicular to the ion beam... 

For a more detailed examination of the value of end-product analysis in ion-molecule kinetic studies, we refer the reader to a recent review. ... 

The selected ion flow tube, SIFT, technique is a fast-flow tube/ion-swarm method for the study of the reactions of ions (positive or negative) with atoms and molecules under truly thermalized conditions over a wide range of temperature. It has been extensively used to study ion-molecule kinetics. Its application to atmospheric and interstellar ion chemistry by several eminent groups over a 20-year period has been crucial to the advancement and understanding of these interesting topics. Recently it has been developed as a very sensitive analytical technique for the detection and quantification of trace gases in air and in human breath down to the ppb level and in real time. 

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