Detachment, electron

Esaulov A V 1986 Electron detachment from atomic negative ions Ann. Phys., Pahs 11 493-592... 

Chalasinski G, Kendall R A, Taylor H and Simons J 1988 Propensity rules for vibration-rotation induced electron detachment of diatomic anions application to NH -> NH + e J. Phys. Chem. 92 3086-91... 

Simons J 1981 Propensity rules for vibration-induced electron detachment of anions J. Am. Chem. See. 103 3971-6 Acharya P K, Kendall R A and Simons J 1984 Vibration-induced electron detachment in molecular anions J. Am. Chem. See. 106 3402-7... 

O Neal D and Simons J 1989 Vibration-induced electron detachment in acetaldehydeenolate anion J. Phys. Chem. 93 58-61... 

Anion photoelectron spectroscopy [37, 38] amd photodetachment techniques [39] provide accurate information on electron detachment energies of negative ions. Ten closed-shell ainions considered here exhibit sharp peaks, indicative of minor or vanishing final-state nuclear rearrangements, in their photoelectron spectra. Comparisons between theory and experiment are straiightforward, for differences between vertical and adiabatic electron detachment energies (VEDEs and AEDEs, respectively) are small. 

Recent work has shown that there are many assumptions required in order to use the silane-cleavage method. However, an advantage of this approach is that it can be nsed to determine acidities at regiospecific positions in very weak acids, including those for which the conjugate base anion is unstable with respect to electron detachment. 

An alternative measure of the electron-donor properties is obtained from the energetics of electron detachment in the gas phase the ionization potentials (IP) of many organic donors have been experimentally determined from the photoelectron spectra obtained by their photoionization in the gas phase. Thus, the values of the ionization potential IP differ from the oxidation potential x by solvation,66 i.e.,... 

Ax = / — x is the ionization potential from the lower state of the line and 0.75 eV is the electron detachment potential of H. [M+/H] = [M/H] + [v], where x is the degree of ionization which changes negligibly while it is close to one, and the electron pressure cancels out. A9 can be identified with A9f obtained by optimally fitting neutral lines with different excitation potentials to one curve of growth (see Fig. 3.13), or deduced from red-infrared colours. As a refinement, a small term [0] should be added to the rhs of Eq. (3.59) to allow for an increase of the weighting function integral towards lower effective temperatures. 

Photoelectron spectroscopy has been used to determine the threshold of electron detachment in small cluster anions and in some cases electronic transitions may be observed. The group of Nakajima and co-workers (261-264) studied several metal sulfide cluster anions. Many other systems have been studied by photoelectron spectroscopy including the [LaCJ (265), [AuC6F6] (266), and mixed-metal cluster anions (267). 

Another approach of this kind uses the approximate Brueckner orbitals from a so-called Brueckner doubles, coupled-cluster calculation [39, 40]. Methods of this kind are distinguished by their versatility and have been applied to valence ionization energies of closed-shell molecules, electron detachment energies of highly correlated anions, core ionization... 

Calculation of ionization energy (electron detachment energy) of the anionic species using P3 method with 6-311++G(2df,2p) basis set. 

Doublet reference states. Some patterns emerge from the calculations with doublet reference states. Table 5.9 presents a summary of all cases involving transitions between singlets and doublets. Ionization energy calculations perform well when a doublet reference state is used. However, electron affinity calculations are advisable only when the doublet reference state is cationic. Even here, it is preferable to reverse the roles of initial and final states by choosing the closed-shell neutral as the reference state in an ionization energy calculation. The P3 method is not suitable for attachment of an electron to a neutral doublet reference state to form a closed-shell anion. It is preferable to choose the anion as the reference state for a P3 calculation of an electron detachment energy. Results for triplets are unpredictable at best. 

In this book, the experts who have developed and tested many of the currently used electronic structure procedures present an authoritative overview of the theoretical tools for the computation of thermochemical properties of atoms and molecules. The first two chapters describe the highly accurate, computationally expensive approaches that combine high-level calculations with sophisticated extrapolation schemes. In chapters 3 and 4, the widely used G3 and CBS families of composite methods are discussed. The applications of the electron propagator theory to the estimation of energy changes that accompany electron detachment and attachment processes follow in chapter 5. The next two sections of the book focus on practical applications of the aforedescribed... 

CgH (n = 6, 7, 8). A novel collision-induced isomerization of CgH7 (10a), which has a sttained allenic bond, to (lOyS) has been reported to occur upon SIFT injection of (10a) at elevated kinetic energies (KE) and collision with helium. In contrast, radical anions (9) and (11) undergo electron detachment upon collisional excitation with helium. Bimolecular reactions of the ions with NO, NO2, SO2, COS, CS2, and O2 have been examined. The remarkable formation of CN on reaction of (11) with NO has been attributed to cycloaddition of NO to the triple bond followed by eliminative rearrangement. 

Anodic oxidation in inert solvents is the most widespread method of cation-radical preparation, with the aim of investigating their stability and electron structure. However, saturated hydrocarbons cannot be oxidized in an accessible potential region. There is one exception for molecules with the weakened C—H bond, but this does not pertain to the cation-radical problem. Anodic oxidation of unsaturated hydrocarbons proceeds more easily. As usual, this oxidation is assumed to be a process including one-electron detachment from the n system with the cation-radical formation. This is the very first step of this oxidation. Certainly, the cation-radical formed is not inevitably stable. Under anodic reaction conditions, it can expel the second electron and give rise to a dication or lose a proton and form a neutral (free) radical. The latter can be either stable or complete its life at the expense of dimerization, fragmentation, etc. Nevertheless, electrochemical oxidation of aromatic hydrocarbons leads to cation-radicals, the nature of which is reliably established (Mann and Barnes 1970 Chapter 3). 

The next topic of our consideration is the ion-radical incipiency. Generally, the mechanism of the ion-radical generation in frozen solution is as follows. Irradiation drives electrons out from a solvent. An organic precmsor (P) transforms into an ion-radical. At first glance, two reactions might be expected to take place electron capture (P -F e P ) and electron detachment (P + e P+ -F 2e). In fact, an indirect redox process takes place, with solvent participation. The example in Scheme 2.41 visualizes 2-methyltetrahydrofman (MeTHF) participation in the redox process, when P is a substance of electron affinity higher than that of the solvent. 

In order to measure the magnitude of the chemical interactions between various ions and buffer gases, approaches that are based on the measurements of either equilibrium or rate constants for ionic processes can be envisioned. An example of a kinetic method is described in the following. The unimolecular kinetic process known as thermal electron detachment (TED) for negative ions (NT -> M + e), should be particularly sensitive to a chemical effect of the buffer gas. This is because the rate of TED will be given by = constant x where the electron... 

This technique has now been applied to many molecular systems, as shown in Fig. S. It can also been applied to van der Waals (vdW) complexes, where often all six intermolecular vibrational modes are observed. Another important application is to anions, where here the electron detachment produces ground-state neutral systems (Fig. 6). The anion state can be... 

The electrical properties of many solids have been satisfactorily explained in terms of the band theory . Briefly, the motion of an electron detached from its parent atom but free to move in a periodically varying potential field, such as that existing between atoms on a crystal lattice, is expressed in terms of a wave function (Boch Function). This particular... 

Electrons in a solid or a liquid may be separated into two groups the core electrons which are the inner, tightly bound electrons with properties sometimes known by studying isolated atom or molecule, and the valence electrons which are the outer, relatively loosely bound electrons. The valence electrons are highly sensitive to the state of aggregation of the system. For our present discussion we might consider as valence electrons the outer 3s electron detached from a sodium atom in liquid ammonia, or the excess electron in a liquid rare gas. 

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