Electron affinity, attachment

To calculate electron production must be balanced against electron depletion. Free electrons in the gas can become attached to any of a number of species in a combustion gas which have reasonably large electron affinities and which can readily capture electrons to form negative ions. In a combustion gas, such species include OH (1.83 eV), O (1.46 eV), NO2 (3.68 eV), NO (0.09 eV), and others. Because of its relatively high concentration, its abUity to capture electrons, and thus its abUity to reduce the electrical conductivity of the gas, the most important negative ion is usuaUyOH . 

The electron affinity of chlorine atoms is +349 kj-mol 1 (see Fig. 1.54), and so we know that 349 k )-mol 1 of energy is released when electrons attach to chlorine atoms to form anions ... 

A positive electron affinity signifies a release of energy when an electron attaches to a gas-phase atom or ion (Section 1.18). 

Phenyltrimethylammonium Ion, N+(CH3)S-CaHe.—In this ion, as in toluene, we ignore the electrons involved in bonds from nitrogen to the attached groups, and consider only the inductive effect. The positive charge on the nitrogen atom increases its electron affinity to a value still greater than that for neutral nitrogen, so that we... 

Hyun et al. [345] prepared PbS Q-dots in a suspension and tethered them to Ti02 nanoparticles with a bifunctional thiol-carboxyl linker molecule. Strong size dependence due to quantum confinement was inferred from cyclic voltammetry measurements, for the electron affinity and ionization potential of the attached Q-dots. On the basis of the measured energy levels, the authors claimed that pho-toexcited electrons should transfer efficiently from PbS into T1O2 only for dot diameters below 4.3 nm. Continuous-wave fluorescence spectra and fluorescence transients of the PbS/Ti02 assembly were consistent with electron transfer from small Q-dots. The measured charge transfer time was surprisingly slow ( 100 ns). Implications of this fact for future photovoltaics were discussed, while initial results from as-fabricated sensitized solar cells were presented. 

Much of what is knotm about the structure response of the ECD is based on empirical observations. Clearly, the ability to correlate the response of the detector to fundamental molecular parameters would be useful. Chen and Wentworth have shorn that the information required for this purpose is the electron affinity of the molecule, the rate constant for the electron attachment reaction and its activation energy, and the rate constant for the, ionic recombination reaction [117,141,142]. in general, the direct calculation of detector response factors have rarely Jseen carried j out, since the electron affinities and rate constants for most compounds of interest are unknown. 

We saw previously that hydrated electrons react very rapidly with the conjugated 1,3-butadiene (k = 8 x 109 M-1 s 1). In less polar solvents the attachment of an electron to 1,3-butadiene (with adiabatic electron affinity of —0.62 eV20) will be slower. The... 

We must be careful with the definition above in many older textbooks, the electron affinity is defined as the energy released when an electron attaches to a neutral atom. This different definition causes (ea) to change its sign. 

The anions originate from the attachment of an electron to whatever electron acceptors are available in the system in bulk hydrocarbon monomer this results in the formation of radical anions. Because the electron affinities of alkenes are much lower than the ionization potentials of hydrocarbon radicals, the neutralization reaction between the cations and the anions, one possible version of which is... 

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. 

The electron affinity (EA) for a molecule is a quantity which is analogous to the ionization energy for cations. Thus, the electron affinity is defined as the negative of the enthalphy change for the electron attachment reaction ... 

A wide range of thermochemical properties can be measured, including not only proton affinity or gas-phase basicity, but also electron affinity, ionization energy, gas-phase acidity and cation affinity Entropy changes upon attachment of an ion to a molecule are also accessible and provide information on both the nature of the bonding and fragmentation mechanisms in cluster ions, especially in biological compounds. Thermochemical determinations by the kinetic method also provide very useful structural information e.g., two-electron three-center bond has been observed in the gas phase by means of the kinetic method. " In the last years, the kinetic method has been also applied to characterize chiral ions in the gas phase. 

The energetics of EC are determined by the electron affinity (EA) of the neutral. The EA is the negative of the enthalpy of reaction of the attachment of a zero kinetic energy electron to a neutral molecule or atom ... 

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