Electron detachment associative

Less is known about Franck-Condon effects on collisional electron detachment from anions. For example, the C-N bond in CH2N02 (1.401 A) is 4.5% longer than the same bond in the CH2N02 anion (1.340 A), and vertical neutralization results in 25-30 kj mol-1 vibrational excitation in the radical, as calculated at several levels of theory [18]. Alkoxy radicals and anions also show different C-0 bond lengths, e.g., 1.317 A and 1.371 A in the 1-pentoxy anion and radical, respectively [1], although the Franck-Condon energies associated with... 

Associative electron detachment has been observed97,98 in the reaction of uranium atoms with oxygen atoms and molecules. The electron detachment cross section is 100 times greater with O atoms than 02 molecules since only 1% of U + 02 collisions detach an electron, while 99% give neutral products UO + O, with a total reaction cross section Q 20 A2. 

In some plasma-chemical systems, the destruction of negative ions by, for example, associative electron detachment is faster than ion-ion recombination ... 

Figure 1 2 1. The different types of 2.5 Lifshitz electronic topological transition (ETT) The upper panel shows the type (I) ETT where the chemical potential EF is tuned to a Van Hove singularity (vHs) at the bottom (or at the top) of a second band with the appearance (or disappearance) of a new detached Fermi surface region. The lower panel shows the type (II) ETT with the disruption (or formation) of a neck in a second Fermi surface where the chemical potential EF is tuned at a vHs associated with the gradual transformation of the second Fermi surface from a two-dimensional (2D) cylinder to a closed surface with three dimensional (3D) topology characteristics of a superlattice of metallic layers...

In denser clouds, however, the abundance of H2 increases rapidly. With gas densities > 102 cm-3 and column densities corresponding to an extinction in the visible of Av > 0.5m hydrogen is expected to be mainly in the molecular form (Werner et al., 1970). Similar results are obtained by de Jong (1972) who also includes low-energy cosmic radiation in his calculations which produces electron densities in dark clouds sufficient to yield H2 formation via associative detachment H- + H -> H2 + e proceeding with a rate constant k v 1.3 x 10 9 cm3 sec-1 at 300 °K. This reaction, however, is only of importance if formation of H2 molecules on grains is for one reason or another inefficient. 

The low effective value for the direct dissociative attachment process was later shown to be due, in part, to the regeneration of electrons via the associative detachment reaction,... 

To test the ECD hypothesis, E. C. M. Chen measured the temperature dependence of the molar response. This entailed a detailed study of all parameters associated with the pulse sampling method. For these molecules the most important reactions were postulated to be electron generation and collection, electron and ion recombination, electron attachment and detachment. It was discovered that the simple thermodynamic model was not applicable and that a kinetic model was necessary to explain the change in temperature dependence. If we assume a steady state exists, an expression can be obtained that relates the ECD molar response to kinetic rate constants for the above reactions [24, 25],... 

The studies into the electrochemical kinetics of solvated electrons were to some extent stimulated by the hypothesis put forward in the second half of 6O s (see Sect. 8) for explaining the role of solvated electrons as intermediate products of electrode reactions, and also by the development made at that time in organic synthesis involving the participation of solvated electrons (see Sect. 9). Undoubtedly, knowledge of the mechanism of electrode generation of solvated electrons is of fundamental importance. Electrochemistry is the chemistry of the electron , Professor A. N. Frumkin once said. In fact, electron reactions at the interface of electronic and ionic conductors are inevitably associated with the electron addition or detachment process. In a solvated electron reaction no heavy particle (atom or molecule) acts as electron acceptor, or donor. In this sense, the electrode reactions of solvated electrons are the most simple electrode processes. Therefore, an insight into the solvated electron reaction mechanism is necessary for electrochemical kinetics as a whole. 

---