Dissociative electron

Considering again the case of a structureless continuum, we have that 8j3 arises from excitation of a superposition of continuum states, hence from coupling within PHmP [69]. The simplest model of this class of problems, depicted schematically in Fig. 5b, is that of dissociation of a diatomic molecule subject to two coupled electronic dissociative potential energy curves. Here the channel phase can be expressed as... 

It was first suggested that the reaction of an alkyl halide with a nickel(I) Schiff base complex yields an alkylnickel(III) intermediate (Equation (56)). Homolytic cleavage of RBr to give an alkyl radical R and a nickel(II) complex (Equation (57)) or, alternatively, one-electron dissociative reduction leading to R (Equation (58)) are possible pathways.254 A mechanism based on the formation of R via dissociative electron transfer of Ni -salen to RX (Equation (59)) has also been proposed.255... 

Sloan PA, Palmer RE (2005) Two-electron dissociation of single molecules by atomic manipulation at room temperature. Nature 434 367... 

As explained by the Franck-Condon diagram, almost no molecular ions will be generated in their vibrational ground state. Instead, the majority of the ions created by El is vibrationally excited and many of them are well above the dissociation energy level, the source of this energy being the 70 eV electrons. Dissociation of... 

A similar process may take place in the reduction of polar compounds with single bonds. A halogen, hydroxy, sulfhydryl or amino derivative by accepting an electron dissociates into a radical and an anion. In aprotic solvents the two radicals combine. In the case of halogen derivatives the result is Wurtz synthesis. In the presence of protons the anion is protonated and the radical accepts another electron to form an anion that after protonation gives a hydrocarbon or a product in which the substituent has been replaced by hydrogen. 

Upon dissolving the metal, a broad optical absorption line appears, peaked at 0.85 eV, and with a tail extending into the visible, which gives the characteristic blue colour (Fig. 10.13). The absorption does not depend on the nature of the solute, showing that the solvated electron dissociated from the cations is responsible for the absorption. The absorption spectrum is almost independent of concentration up to 10 1 MPM. 

Another series of reactions (Nos 8-15) show different possibilities for the addition of conjugated double bonds on a P(III) atom. Although this type of reaction has been stated to be a concerted six-electron dissociative process, and therefore stereoselective, its scope is limited by the fact that it cannot be generalized to all P(III) compounds as some of them are fairly unreactive, or yield phosphonium salts or may even be dealkylated. 

An especially important result from these studies is that a,j is remarkably independent of the complexity of the reacting ions (in marked contrast to electron dissociative recombination), only varying over the limited range (4-10) x 10 8 cm3 s-1 at 300 K, even for ions as different as those involved in reactions (67) and (71). This coupled with the relatively weak temperature dependence of ari in practice allows a single value for ari ( 6 x 10-8 cm3 s 1) to be used for all mutual neutralization reactions in ionospheric de-ionization calculations without introducing serious errors. This value is in close accordance with estimates of ionic recombination coefficients obtained by Ulwick211 from observations of ionization production and loss rates in the atmosphere in the altitude region 50-75 km. 

Table 5.8.5. Experimental and calculated (in brackets) Ng-M bond lengths and stretching frequencies v as well as computed electronic dissociation energies De for the Ng-M bonds in NgMX complexes...

The ion-electron dissociative recombination-rate constant of reaction (42) has been measured 9 and was found to be approximately 4 X 10 7 ion-1 cc. sec."1. 

Electron affinity (EA) is a measure of the ability of a molecule to attach an electron. This value is equal to an adiabatic IE of the corresponding negative ion. EAs for some EHal2 have been derived from appearance energies of the corresponding anions formed by low-energy electron dissociative resonance capture from in the conrse... 

The nonlinear phenomena in intense magnetic and laser fields are given some prominence in this volume. Two chapters deal with multiphoton processes and time-dependent phenomena in atoms. In another chapter it is emphasized that the process of multi-electron dissociative ionization of molecules offers considerable challenges both for modeling and for the study of first-principles. The dynamics of molecules in such intense laser fields is an area of great interest, both at the time of writing and for future studies. In all these chapters the interplay between theory and experiment is demonstrated. 

Figure 4.8 In (a) the principle oftransition state spectroscopy is shown. A continuous wave UV laser pulse with a frequency exceeding the energy gap between anionic potential (XHXq and neutral potential (XHX) is employed. After photodetachment of the electron, dissociation will occur equally in the two possible channels XH-tX and Xt-HX. In (b)...

The performance of the Hartree-Fock model is illustrated in Table 1, where we have listed the electronic dissociation energy (De), the equilibrium bond distance (re), and the harmonic (coe) and fundamental (v) frequencies calculated at the Hartree Fock/cc-pVXZ levels. Basis set convergence is in all cases rapid. Compared with the... 

Table 1 Calculations of the Electronic Dissociation Energy De (kJ/mol), the Equilibrium Geometry re (pm), and the Harmonic e (cm-1) and Fundamental v (cm-1) Vibrational...

The observation 185) on tantalum ribbons that, under controlled conditions, quantities of CO up to 300 monolayers can be taken up by the metal and then desorbed as molecular CO, indicates clearly that on this system at least, the CO molecule is able to be incorporated into the bulk. The suggestion 66) that on tungsten, only the substate contributes to the electron dissociative ionic cross-section of the phase, also does nothing to contradict the possibility of adsorbed CO molecules within the 2 a-nd jSg substates being closely associated with the electron well of the bulk metal. If this is the case, any ions produced by electronic interactions would be unable to leave the surface before neutralization by the electrons of the metal. 

For chemical etching, polyatomic halogen-bearing molecules are often used. Electron collisions with these molecules often lead to negative ions through electron dissociative attachment,... 

Oxygen ionized by electrons dissociates into oxygenated depleted ceramic lattice... 

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