Charge transfer reaction cross section measurement

Fig. 13. Polar differential cross section (CM-system) for the charge transfer reaction Na + 1 - Na+ + 1. Notice the relative shift of the zero point of both curves and the multiplication factors of different parts of the curves. At the top the angular resolution of the measurements is indicated. (Delvigne and Los, 1973.)...

Finally, a comprehensive study of the thermochemistry of sulfur fluoride cations and neutrals was performed (Fisher et al., 1992). Endothermic charge-transfer reactions of several of the SF+ ions were examined. Analyses of these cross sections yielded the ionization energies of SF from reactions with Xe of SF3 from reactions with CH3I, NO, and C HsBr of SF4 from reactions with Xe and O2 and of SF5 from reactions with NO, C6H5CF3, and CH3I. IE(SF2) was not measured in our work, as a precise photoelectron value (10.08 0.05 eV) was already available in the literature (DeLeeuw et al., 1978). Some of our values... 

The major application of this technique, principally by Lindholm and co-workers (see Chapter 10), has capitalized on the above limitation in a study of charge-transfer processes, where the products may exhibit a thermal energy distribution. Even in this application, cross sections are difficult to obtain because the sampling volume is not well defined. Lindholm has been careful to quote only Q values which are estimates of the relative reaction efficiencies. There is another reason why any such cross section so measured may be unreliable. It is plausible, and indeed it has recently been demonstrated, that charge-transfer reactions may yield some products which are forward-scattered in the laboratory framework these would result from collisions with small impact parameters. To the extent that these products will not be detected in a transverse tandem machine, the measured cross section will be underestimated. 

The most detailed probe of an ion-molecule reaction is the state-to-state cross section. The measurement of angularly resolved state-to-state cross sections has been achieved only for reactants in their ground state, but true state-to-state total cross sections have now been measured in a few favorable cases. A particularly novel method for product state determination with reactant state selection has been developed by Ng. In the differential reactivity method, product vibrational states are distinguished by their differing cross sections for charge transfer with selected molecules. The charge transfer reaction... 

In this presentation we will report on the total reactive cross section measurements of the reaction of F with molecular hydrogen and its isotopic variants, on some charge transfer processes and on the angular.and energy variation of the FD products from the reaction F (D2 D)FD. Som preliminary cross section measurements for some reactions of F with CH. will also be mentioned. 

Probably the simplest reaction of a gaseous positive ion is charge transfer. Fig. 2 gives the cross section measurement of... 

The major problem in method (a) is that in ion-molecule interchange, considerable momentum in the direction of travel of the incident ion is imparted to both final products. Hence, in a perpendicular type apparatus only transfer of low weight particles can be observed at all and only at very low velocities of the incident ions (1, 9, 10, 11, 12, 13, 19, 20, 23, 27). Cross-sections cannot be measured. The value of these investigations is that some ion-molecule reactions—e.g., proton transfer and hydride ion transfer—can be identified. The energetics and the competition between charge exchange and ion-molecule reactions can be discussed, and by using partially deuterated compounds, one can obtain a detailed picture of the reaction. 

There is a growing tendency to invoke surface states to explain electron transfer at semiconductor-electrolyte interfaces. Too frequently the discussion of surface states is qualitative with no attempt to make quantitative estimates of the rate of surface state reactions or to measure any of the properties of these surface states. This article summarizes earlier work in which charge transfer at the semiconductor-electrolyte interface is analyzed as inelastic capture by surface states of charge carriers in the semiconductor bands at the surface. This approach is shown to be capable of explaining the experimental results within the context of established semiconductor behavior without tunneling or impurity conduction in the bandgap. Methods for measuring the density and cross section of surface states in different circumstances are discussed. 

Here the N-f ion is prepared in vibrational level v of either the X2 g+ or A 2IIU electronic state. This reaction of state-selected N2+ ions has been the subject of many other experimental [3, 4] and theoretical [5-8] studies. We have also measured charge-transfer cross sections for the reaction [9, 10]... 

For this system at low energies the major product channel is chemical reaction to give N2H+ + H, and it is interesting to study the competition between the two product channels. At the same time we measured charge transfer cross sections for Ar+(2P3/2,2P1/2) colliding with H2. The third type of ion-molecule system we have studied is [11]... 

O Reactions.—The cross-section for charge transfer between O- ions and 02(3Sy ) has a maximum value of 7.8 x 10-1 cm2 at an energy of 5 keV of the incident ion,289 whereas that for O- and 02(1A4,) was less than 1 x 10-1 cm2. Reaction rate-constants for reactions of O-, OH-, 02-, Cl-, C03-, and 0H-(H20) with H20 have been measured, and association rate-constants for several ions with COa and S02 tabulated.290 The rate of formation of NO+ by the reaction of 0+ with N2 has been commented upon.291 The formation of H02+ and Os+ by the reaction of 02+( 4 ) with H2 and 02 has been reported,292 and 02+-02, NO+-NO interactions have been considered.293 Rate-constants for reactions of O o4 ,) with N2, Ar, Cl, C02, H2, and 02 have been reported,294 and electron-transfer transitions during the collision of 02, N2, NO, and CO with their respective ions discussed.295 The nearly resonant process (107) has been shown not to occur with high efficiency.29 The lifetime of the 3 state of OH+ has been shown to be 900 ns.87... 

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