Monte-Carlo simulation of microwave noise in n-type InSb

Numerical Monte Carlo calculations of the electron noise temperature dependence on the electric field strength in n-type InSb are presented. It is established that hot electron noise temperature in strongly compensated InSb increases with the increase of electron density due to more intensive electron–electron scattering stimulating delocalization of electrons from the bottom of the conduction band. For low electron density, when the electron–electron scattering is negligibly small, the electron noise temperature is found to become close to the lattice temperature in a wide range of electric field strength in which the electron gas cooling effect takes place. Satisfactory agreement between calculations of the electron noise temperature and available experimental data has been obtained.     

Tunneling of excess electron from free and trapped states

The association of an excess electron with scavengers in nonpolar solvents is considered assuming that the free electron performs the free diffusion during the lifetime between sequential places of temporary localization. The reaction of a free electron during this motion is at first taken into account along with a tunneling of the localized electron. When the mean step length between sequential localizations is short the reaction of the excess electron is diffusional and the free state contribution to the total reaction rate is negligible. In the opposite case, when this reaction becomes essentially hopping, the corresponding rate is significantly accelerated due to a faster diffusion of the free electron.     

Photo-Induced Intermolecular Electron Transfer-Effect of Acceptor Molecular Structures

Photo-induced electron transfer versus molecular structure of acceptors is investigated using ultrafast time-resolved transient grating spectroscopy. Typical laser dyes Rhodamine 101 (Rh101) and Rhodamine 6G (Rh6G) in electron donor solvent-aniline are adopted as the objects. The forward electron transfer time constant from aniline to the excited singlet state of two Rhodamine dyes and subsequent back electron transfer from two dyes to aniline are measured. The experimental results denote that Rh6G presents faster electron transfer rates with aniline in both forward electron transfer and back electron transfer processes. With chemical calculation and qualitative analysis, it is found that the flexible molecular geometry of Rh6G leads to stronger electron coupling with donor solvent and further gives rise to larger electron transfer rates.     

Electron transfer versus proton transfer in gas-phase ion/ion reactions of polyprotonated peptides

The ion/ion reactions of several dozen reagent anions with triply protonated cations of the model peptide KGAILKGAILR have been examined to evaluate predictions of a Landau-Zener-based model for the likelihood for electron transfer. Evidence for electron transfer was provided by the appearance of fragment ions unique to electron transfer or electron capture dissociation. Proton transfer and electron transfer are competitive processes for any combination of anionic and cationic reactants. For reagent anions in reactions with protonated peptides, proton transfer is usually significantly more exothermic than electron transfer. If charge transfer occurs at relatively long distances, electron transfer should, therefore, be favored on kinetic grounds because the reactant and product channels cross at greater distances, provided conditions are favorable for electron transfer at the crossing point. The results are consistent with a model based on Landau-Zener theory that indicates both thermodynamic and geometric criteria apply for electron transfer involving polyatomic anions. Both the model and the data suggest that electron affinities associated with the anionic reagents greater than about 60-70 kcal/mol minimize the likelihood that electron transfer will be observed. Provided the electron affinity is not too high, the Franck-Condon factors associated with the anion and its corresponding neutral must not be too low. When one or the other of these criteria is not met, proton transfer tends to occur essentially exclusively. Experiments involving ion/ion attachment products also suggest that a significant barrier exists to the isomerization between chemical complexes that, if formed, lead to either proton transfer or electron transfer.     

Molecular integrals of relativistic effects with gaussian-type orbitals

A mathematical analysis is presented of molecular integrals of relativistic interactions in molecules. The integrals are based on Gaussian-type orbitals and include those arising from variation of electron mass with velocity, one-electron Fermi contact interaction, electron spin-same-orbit interaction, electron spin-nuclear spin interaction, electron spin-spin contact interaction, electron spin-other-orbit interaction, electron spin-spin dipolar interaction and electron orbit-orbit interaction. The integrals are expressed in suitable forms for use in computer. It is also pointed out that the integrals are written essentially in terms of the overlap, nuclear attraction, electron repulsion, or field integrals.     

Substituent effect on redox potential of nitrido technetium complexes with Schiff base ligand: Theoretical calculations

Theoretical calculations based on the density functional theory (DFT) were performed to understand the effect of substituents on the molecular and electronic structures of technetium nitrido complexes with salen type Schiff base ligands. Optimized structures of these complexes are square pyramidal. The electron density on a Tc atom of the complex with electron withdrawing substituents is lower than that of the complex with electron donating substituents. The HOMO energy is lower in the complex with electron withdrawing substituents than that in the complex with electron donating substituents. The charge on Tc atoms is a good measure that reflects the redox potential of [TcN(L)] complex.     

An Electron‐Deficient Building Block Based on the B←N Unit: An Electron Acceptor for All‐Polymer Solar Cells

A double B←N bridged bipyridyl (BNBP) is a novel electron‐deficient building block for polymer electron acceptors in all‐polymer solar cells. The B←N bridging units endow BNBP with fixed planar configuration and low‐lying LUMO/HOMO energy levels. As a result, the polymer based on BNBP units (P‐BNBP‐T) exhibits high electron mobility, low‐lying LUMO/HOMO energy levels, and strong absorbance in the visible region, which is desirable for polymer electron acceptors. Preliminary all‐polymer solar cell (all‐PSC) devices with P‐BNBP‐T as the electron acceptor and PTB7 as the electron donor exhibit a power conversion efficiency (PCE) of 3.38 %, which is among the highest values of all‐PSCs with PTB7 as the electron donor.     

New perspective of electron transfer chemistry

A new perspective of electron transfer chemistry is described for fine control of electron transfer reactions including back electron transfer in the charge separated state of artificial photosynthetic compounds and its synthetic application. Fundamental electron transfer properties of suitable components of efficient electron transfer systems are described in light of the Marcus theory of electron transfer, in particular focusing on the Marcus inverted region, and they are applied to design multi-step electron transfer systems which can well mimic the function of a photosynthetic reaction center. Both intermolecular and intramolecular electron transfer processes are finely controlled by complexation of radical anions, produced in the electron transfer, with metal ions which act as Lewis acids. Quantitative measures to determine the Lewis acidity of a variety of metal ions are given in relation to the promoting effects of metal ions on the electron transfer reactions. The mechanistic viability of metal ion catalysis in electron transfer reactions is demonstrated by a variety of examples of chemical transformations involving metal ion-promoted electron transfer processes as the rate-determining steps, which are made possible by complexation of radical anions with metal ions.     

Electron localization functions and local measures of the covariance

The electron localization measure proposed by Becke and Edgecombe is shown to be related to the covariance of the electron pair distribution. Just as with the electron localization function, the local covariance does not seem to be, in and of itself, a useful quantity for elucidating shell structure. A function of the local covariance, however, is useful for this purpose. A different function, based on the hyperbolic tangent, is proposed to elucidate the shell structure encapsulated by the local covariance; this function also seems to work better for the electron localization measure of Becke and Edgecombe. In addition, we propose a different measure for the electron localization that incorporates both the electron localization measure of Becke and Edgecombe and the Laplacian of the electron density; preliminary indications are that this measure is especially good at elucidating the shell structure in valence regions. Methods for evaluating electron localization functions directly from the electron density, without recourse to the Kohn-Sham orbitals, are discussed.     

Electron beam potential depression as an ion trap in Fourier transform ion cyclotron resonance mass spectrometry

Trapping of ions in the electron beam of a FTICR mass spectrometer is investigated and a simple model describing the confinement process is presented. Detection of resistive-wall destabilization of the magnetron motion of ions in the trapped-ion cell is used to determine conditions for ion trapping within and escape from the electron beam. The model predicts a potential well that is dependent on electron beam current, energy, and dimension in defining its capacity for low energy ions. Plots of ion retention time versus ion number are consistent with a model in which ions are initially trapped in the electron beam but with increasing ion formation will eventually overcome the potential depression in the electron beam and escape into magnetron orbits. Based upon this model, expressions are derived for ion retention time which are then fit to the experimental data. The model is used to estimate ion number, initial magnetron radius and ion cloud shape and density. One example in which electron trapping is important in the FTICR experiment is in the efficient transfer of ions between dual trapped-ion cells. Ion transfer within the potential depression of the electron beam environment is shown to be virtually 100% efficient over a 10 ms interval whereas all ions are lost to collisions with the conductance limit after 2 ms when transferring without the confining aid of the electron beam. Several analytical applications of electron traps in the ICR cell are now being investigated.     

Mitigating Electron Leakage of Solid Electrolyte Interface for Stable Sodium-Ion Batteries

The interfacial stability is highly responsible for the longevity and safety of sodium ion batteries (SIBs). However, the continuous solid-electrolyte interphase(SEI) growth would deteriorate its stability. Essentially, the SEI growth is associated with the electron leakage behavior, yet few efforts have tried to suppress the SEI growth, from the perspective of mitigating electron leakage. Herein, we built two kinds of SEI layers with distinct growth behaviors, via the additive strategy. The SEI physicochemical features (morphology and componential information) and SEI electronic properties (LUMO level, band gap, electron work function) were investigated elaborately. Experimental and calculational analyses showed that, the SEI layer with suppressed growth delivers both the low electron driving force and the high electron insulation ability. Thus, the electron leakage is mitigated, which restrains the continuous SEI growth, and favors the interface stability with enhanced electrochemical performance.     

Characterization of a Co-CoO obliquely evaporated magnetic tape by analytical electron microscopy and electron holography.

The microstructure and magnetic domain structure of a Co-CoO obliquely evaporated tape for magnetic recording are studied by analytical electron microscopy and electron holography, respectively. While the existence of Co and CoO crystallites is confirmed by energy-filtered electron diffraction, columnar structure of the Co crystallites surrounded by the densely packed CoO crystallites is visualized by an elemental mapping method with electron energy loss spectroscopy, and the crystal orientation relation among the Co crystallites is clarified by high-resolution electron microscopy. It is found that the neighboring Co crystallites have close crystal orientations. On the other hand, electron holography reveals the magnetic flux distribution in a thin section of the tape. Although there exists the background resulting from the effect of inner potential with thickness variation, the distribution of lines of magnetic flux is found to correspond well to the recorded pattern.     

Evidence for a mechanism that involves secondary electron capture in the liquid secondary ionization mass spectrometry beam-induced dehalogenation of organic compounds

The effect of the analyte electron affinity on the liquid secondary ionization mass spectrometry beam-induced dehalogenation of simple bromoaromatic compounds in a glycerol matrix was investigated. The results show a definite trend of decreasing dehalogenation with increasing analyte electron affinity. At high analyte electron affinity (≥ 1.0 eV), no dehalogenation was observed. These results are consistent with electrochemical and pulse radiolysis studies where one electron reduction was shown to be responsible for dehalogenation. A chloroaromatic compound with high electron affinity, 4-(4-chloro-benzoyl)pyridine, exhibited reduction by hydrogen addition but not dehalogenation. The radiation chemistry of alcohols was used to elaborate a scheme of the reactive species generated in the glycerol matrix by kiloelectronvolt particle bombardment. The possible role of those species in reduction processes such as dehalogenation was evaluated. The observation that dehalogenation decreases with analyte electron affinity is mechanistically consistent with the proposition that secondary electron production is an intrinsic part of the bombardment process.     

Theoretical study on two types of weak interactions between methylenecyclopropane and XY (X,Y = H,F, Cl,and Br)

We present theoretical evidence that the two types of interactions exist in the complexes formed between methylenecyclopropane (MECP) and XY (X, Y = H, F, Cl, and Br). Two seats of XY interacted with MECP are located: (a) is via the pseudo‐π bonding electron pair associated with a C? C bond of the cyclopropane ring and (b) is via the typical‐π bonding of electron pair of the C?C bond of MECP. These two types of weak interactions are compared based on the calculated geometries, interaction energies, frequency changes, and topological properties of electron density. The integration of electron density over the interatomic surface is found to be a good measure for the strength of weak interaction. Furthermore, the total electron density and separated σ and π electron densities are also computed and discussed in this article. The separated electron density shows σ electron density determined the strength and π electron density influenced the direction of the hydrogen/halogen bond. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Spectroscopic imaging techniques for characterization of polymer morphologies: a combination of infrared and electron microscopy

The morphological characterization of polymer blends consisting of polyamide and poly(tetrafluoroethylene) using FT-IR spectroscopy and electron microscopy is described. To enhance the lateral resolution - one of the main limits in infrared spectroscopy - a combination with scanning electron microscopy and analytical electron microscopic methods of a transmission electron microscope was made. The possibilities of electron energy loss spectroscopy and energy filtered transmission electron microscopy (EFTEM) in the area of polymer characterization are outlined.     

Correlation of molecular properties with the electron-interaction parameters of functional groups

It is shown that it is possible to correlate the properties of Y in XZY or XY, as affected by X in position m or p with respect to Y, with quantities that reflect the changes in response to X in the electron energies of the top filled and lowest empty orbitals of Y. The magnitude of the change in electron density in the orbitals of Y is the same when X is an electron donor (density increase) or electron acceptor (density decrease).     

Non-nuclear attractor of electron density as a manifestation of the solvated electron

Two or more polar molecules can trap an excess electron either in a dipole-bound fashion where it is located outside of the cluster (dipole-bound electron) or inside the cluster (solvated electron). The topology of the electron density in dipole-bound and solvated-electron clusters has been examined for the paradigm (HF)3- cluster. As spatial confinement of the excess electron increases, a non-nuclear maximum (or attractor) of the electron density eventually forms, which suggests that the solvated electron can be described as a topological atom with its own set of physicochemical properties.     

Correlation study of Franck-Condon barriers associated with electron self-exchange reactions with ionization potentials and electron affinities and experimental Born-Oppenheimer potentials

An accurate theoretical scheme for obtaining directly the Franck-Condon barrier associated with the electron self-exchange reaction from ionization potentials and electron affinities is presented. Applicability is tested using some diatomic molecular redox couples. The corresponding ionization potentials and electron affinities are obtained from the Born-Oppenheimer potential energy curves which are directly determined from the experimental vibration-rotational spectroscopic data. The Franck-Condon barriers are calculated for the electron self-exchange reactions and are also compared with those from other theoretical methods.     

Ab initio molecular dynamics simulation of a medium-sized water cluster anion: from an interior to a surface-located excess electron via a delocalized state

We present a computational study of the structure and dynamics of an excess electron in a medium-sized water cluster aimed at addressing the question of interior vs exterior solvation. Ab initio Born-Oppenheimer molecular dynamics simulations were performed within the DFT framework, employing a hybrid Gaussian and plane-wave formalism together with the PBE exchange-correlation functional and norm-conserving pseudopotentials. Analysis of a 15-ps trajectory allowed us to reach the following conclusions: (i) the excess electron is predominantly located at the cluster surface (even if it is initially placed in the interior), (ii) the computed electron binding energies correlate with the electron localization rather than with its bulk vs surface location, and (iii) a dynamical interconversion between two different H-bond patterns around the electron occurs. The computed electron binding energies and the most relevant features of the IR spectrum are in a very good agreement with results of previous experimental studies.