Flow systems, afterglow techniques

FA techniques, see Flowing afterglow techniques /-block metallaboranes future research, 3, 257 overview, 3, 133-174 /-block metallacarboranes characteristics, 3, 246 overview, 3, 175-264 FBS, see Fluorous biphasic system [5,5,5,5]-Fenestranes, via carbonylative carbocyclization,... 

More recently ion cyclotron resonance (ICR) mass spectrometric techniques have been applied to proton transfer equilibria measurements [8, 9]. One advantage of this method is the in situ determination of the ion concentrations. The reaction chamber is the resonance cavity in which the microwave absorption by the ions is measured. The method works only at low pressures / <10 torr and has been used only at room temperature. Clustering reactions like (3) are kinetically third order at low pressures since they require a third body collision for stabilization of the exothermic association product of the reaction. Therefore they are too slow for equilibrium determinations by ICR. The flowing afterglow technique which uses a flow rather than a stationary reaction system, and external ion sampling (as in the Alberta apparatus) has been also used with very good success for ion equilibria measurements [10,11]. 

In the present review, a new variation on an existing experimental method will be used to show how accurate unimolecular dissociation rate constants can be derived for thermal systems. For example, thermal bimolecular reactions are amenable to study by use of several, now well-known, techniques such as (Fourier transform) ion cyclotron resonance spectrometry (FTICR), flowing afterglow (FA), and high-pressure mass spectrometry (HPMS). In systems where a bimolecular reaction leads to products other than a simple association adduct, the bimolecular reaction can always be thought of as containing a unimolecular... 

Three basic techniques, and variations thereof, have been used in recent years to study aspects of gas-phase ion-molecule reactions pertinent to organic systems they are ion cyclotron resonance spectrometry, flowing afterglow, and high pressure mass spectrometry. The essential feature of these techniques is that ions produced under vacuum are allowed to undergo from few to many collisions with neutrals before they are neutralized at the walls of the instrument. 

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