Fundamental electron

Molecular transport junctions differ from traditional chemical kinetics in that they are fundamentally electronic rather than nuclear - in chemical kinetics one talks about nucleophilic substitution reactions, isomerization processes, catalytic insertions, crystal forming, lattice changes - nearly always these are describing nuclear motion (although the electronic behavior underlies it). In general the areas of both electron transfer and electron transport focus directly on the charge motion arising from electrons, and are therefore intrinsically quantum mechanical. 

Silicon is a model for the fundamental electronic and mechanical properties of Group IV crystals and the basic material for electronic device technology. Coherent optical phonons in Si revealed the ultrafast formation of renormalized quasiparticles in time-frequency space [47]. The anisotropic transient reflectivity of n-doped Si(001) featured the coherent optical phonon oscillation with a frequency of 15.3 THz, when the [110] crystalline axis was parallel to the pump polarization (Fig. 2.11). Rotation of the sample by 45° led to disappearance of the coherent oscillation, which confirmed the ISRS generation,... 

Measurements of the optical properties in this range of wavelengths can probe the fundamental electronic transitions in these nanostructures. Some of the aforementioned effects have in fact been experimentally revealed in this series of experiments (90). As mentioned above, the IF nanoparticles in this study were prepared by a careful sulfidization of oxide nanoparticles. Briefly, the reaction starts on the surface of the oxide nanoparticle and proceeds inward, and hence the number of closed (fullerene-like) sulfide layers can be controlled quite accurately during the reaction. Also, the deeper the sulfide layer in the nanoparticle, the smaller is its radius and the larger is the strain in the nanostructure. Once available in sufficient quantities, the absorption spectra of thin films of the fullerene-like particles and nanotubes were measured at various temperatures (4-300 K). The excitonic nature of the absorption of the nanoparticles was established, which is a manifestation of the semiconducting nature of the material. Furthermore, a clear red shift in the ex-citon energy, which increased with the number of sulfide layers of the nanoparticles, was also observed (see Fig. 21). The temperature dependence of the exciton... 

Using the more advanced quantum chemical computational methods it is now possible to determine the fundamental electronic properties of zeolite structural units. The quantum chemical basis of Loewenstein s "aluminum avoidance" rule is explored, and the topological features of energy expectation value functionals within an abstract "nuclear charge space" model yield quick estimates for energy relations for zeolite structural units. 

From Bohr s postulates, it is possible to derive the energies of the possible stationary states responsible for the radiation that is absorbed or emitted by an atom consisting of a single electron and nucleus. The specification of these states permits one to then compute the frequency of the associated electromagnetic radiation. To begin, one assumes the charge on the nucleus to be Z times the fundamental electronic charge, e, and that Coulomb s law provides the attractive force, F, between the nucleus and electron ... 

The Perrin-Jablonski diagram (Figure 3.1) is convenient for visualizing in a simple way the possible processes photon absorption, internal conversion, fluorescence, intersystem crossing, phosphorescence, delayed fluorescence and triplet-triplet transitions. The singlet electronic states are denoted S0 (fundamental electronic state), Si, S2,... and the triplet states, Ti,T2,. Vibrational levels are associated with each electronic state. It is important to note that absorption is very fast ( 10 15 s) with respect to all other processes (so that there is no concomitant... 

It is conceivable that the presence of such complications must affect the shape of the cyclic voltammograms, and hence perturb to some extent the diagnostic criteria for the above-mentioned fundamental electron transfer processes. As these reactions proceed at their own rates, cyclic voltammetry will be able to detect them only if their rates fall within the time scale of the voltammetric technique (which ranges from a few tens of seconds to a few milliseconds). 

A number of excellent reviews and books have included consideration of the fundamental electron impact ionization process, and the attention afforded the experimental measurement of ionization potentials and Augment ion appearance energies over the years is reflected in the comprehensive database of ionization potentials and gas phase ion enthalpies of formation published through the National Bureau of Standards in printed and electronic forms. In contrast, few absolute ionization cross sections have been measured. The most comprehensive compilation of molecular ionization cross sections are relative values measmed with a modified commercial electron impact mass spectrometer ion source using the cross section for Ar as a reference. ... 

A.L. Albert, "Fundamental Electronics and Vacuum Tubes , Macmillan,NY(1947)... 

In the second case, reading eq.(26), it is necessary that at least one of the Q-space states has the same parity as the operator p. Then, in (26) there may be a non-zero off-diagonal element connecting the ingoing to the outgoing channels. This state is called here a transition state (TS) and the coordinates of the stationary arrangement of external Coulomb sources a°TS (or otTS) is defined as a transition state structure (TSS). The TSS is a fundamental electronic property, while the quantum states of the TS include translational and rovibrational states with their characteristic density of states. 

Fig. 2. Electronic dipolar nature of the peptide unit. The numbers adjacent to each atom give the approximate fractional electronic charge attributed to each atom (in units of fundamental electronic charge). The magnitude of the dipole moment is 0.72 ek = 3.46 D.

Carbon-based nanotubes (CNTs) have attracted a great deal of attention in the fields of chemistry, physics, and materials science and have been extensively studied since their initial discovery in 1991.36 Much of the excitement in this area of research stems from their unique structures, fundamental electronic and physical properties, and potential applications.37 Inspired by these carbon nanotube studies, coordination chemists have undertaken significant efforts toward the construction of tube-like complexes through metal-ligand coordination.38 1 Examples of silver(I) tubular complexes obtained via assembly reactions of predesigned organic ligands with silver salts are described here.42-44... 

Least motion effects are often energetically small and vary in importance with the nature of the transition state they are frequently overridden by other factors. Therefore, even though the predictions of ALPH and PLNM are equivalent, the fact that ALPH/PLNM fails implies that the physical basis of the observed effects is not a supposedly fundamental electronic dogma like ALPH. 

The formation of charge domains showed that the fundamental electron transfer process involves a high number of surface sites. The tribo-electric charging of polymers has to be considered as a collective phenomenon. 

Many textbooks say that alkyl groups are fundamentally electron-donating and thus stabilize cations. This statement does contain some truth but it is important to understand the way in which they really donate electrons—weakly by a conjugation into empty p orbitals. 

The difference between metals and semiconductors is, fundamentally, electronic in origin. In a metal, overlap of atomic or ionic orbitals on neighbouring sites leads to a continuum of levels that are only partially occupied by electrons. There are, therefore, energy levels immediately above the topmost occupied level that are empty and easily accessible thermally and the ability of electrons to move freely into these levels gives rise to the characteristic properties associated with a metal, such as conductivity, reflectivity etc. 

A high level of effort on die investigation of semiconductor surfaces was sustained by the growing realization that the electronic properties of semiconductor surfaces are quite different from the bulk properties, that they determine to a large extent the characteristics of semiconductor devices, and that they are very sensitive to the various ambients. It should also be kept in mind that fundamental electronic properties of the bulk are in many Instances studied through contact with the surface. 

Recent development of the computational technique for electronic state of materials enables us to calculate the accurate valence electronic structure of fairly large and complicated systems from the first principles. However, it is still very important to investigate the electronic state and chemical bonding of a simple and small cluster model of metal element, because the basic imderstanding of the essential properties of the metal elements is not sufficient. It is also very useful to investigate a small cluster model in understanding various kinds of properties and phenomena of more complicated metallic materials like alloys and intermetallic compounds, because the fundamental electronic state is reflected in their properties. 

A discussion of the chemical behavior of metals on the basis of their fundamental electronic properties and how they affect metal processing... 

Several scales presented in Table 3 show promise as measures of fundamental electronic properties of amino acids as does the Hp index of hydrophilicity. Nevertheless, additional improvements are desirable. The polarizability index of steric effects should include hyperconjugation as a component. Clearly, the movement of electrons into antibonding orbitals contributes to molecular deformation (24). The Hp index is based on PM3 calculations of electron densities for the component atoms of amino acid side chains. A more integrative approach with higher-order theory is likely to refine this measure additionally. 

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