Different Energies (different + energy)

Distribution by Scientific Domains

Selected Abstracts

Focused-Ion-Beam-Based Selective Closing and Opening of Anodic Alumina Nanochannels for the Growth of Nanowire Arrays Comprising Multiple Elements,

Nai-Wei Liu
A lithographic process based on focused ion beam bombardment is developed for selectively closing and opening nanochannels on a porous anodic alumina film. This resist-free process is based on the use of focused ion beams with different energies that strike a balance between material sputtering and material relocation. This process is used to selectively grow nanowire patterns of different elements. [source]

Davydov's solitons in zigzag carbon nanotubes

Larissa Brizhik
Abstract Nonlinear mechanism of charge transport in low-dimensional nanosystems is considered, based on the account of the electron,phonon interaction that arises from the deformation dependencies of the on-site and the hopping interaction energies at intermediatevalues of the corresponding coupling constants. In particular, carbon-type hexagonal zigzag nanotubes are studied. It is shown that in the adiabatic approximation the electron,phonon coupling results in the self-trapping of carriers and formation of polaron (soliton) states. We show that the ground state of an electron in a nanotube is a low-dimensional polaron whose symmetry depends on the strength of the coupling. Namely, at relatively weak coupling, the polaron possesses quasi-one-dimensional properties and has an azimuthal symmetry. When the coupling constant exceeds some critical value, the azimuthal symmetry breaks down and two-dimensional polaron on the nanotube surface is formed. There are also polarons formed by the electrons in the conducting band (or by holes in the valence band) in semiconducting zigzag carbon nanotubes. Such polarons are described by the system of coupled nonlinear Schroedinger equations which admits single-band polarons, and entangled (hybridized) polarons. These two types of polarons possess different energies and symmetry properties. Single-band solutions are one-dimensional polarons: they are azimuthally symmetric and localized along the nanotube axis. The entangled polarons are also self-trapped along the nanotube axis, but possess an inner structure and are modulated around the nanotube. The entangled polarons break the azimuthal symmetry and their energy is lower than the energy of single-band polarons. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source]

Spin densities in two-component relativistic density functional calculations: Noncollinear versus collinear approach

Christoph Van WüllenArticle first published online: 3 APR 200
Abstract With present day exchange-correlation functionals, accurate results in nonrelativistic open shell density functional calculations can only be obtained if one uses functionals that do not only depend on the electron density but also on the spin density. We consider the common case where such functionals are applied in relativistic density functional calculations. In scalar-relativistic calculations, the spin density can be defined conventionally, but if spin-orbit coupling is taken into account, spin is no longer a good quantum number and it is not clear what the "spin density" is. In many applications, a fixed quantization axis is used to define the spin density ("collinear approach"), but one can also use the length of the local spin magnetization vector without any reference to an external axis ("noncollinear approach"). These two possibilities are compared in this work both by formal analysis and numerical experiments. It is shown that the (nonrelativistic) exchange-correlation functional should be invariant with respect to rotations in spin space, and this only holds for the noncollinear approach. Total energies of open shell species are higher in the collinear approach because less exchange energy is assigned to a given Kohn-Sham reference function. More importantly, the collinear approach breaks rotational symmetry, that is, in molecular calculations one may find different energies for different orientations of the molecule. Data for the first ionization potentials of Tl, Pb, element 113, and element 114, and for the orientation dependence of the total energy of I and PbF indicate that the error introduced by the collinear approximation is ,0.1 eV for valence ionization potentials, but can be much larger if highly ionized open shell states are considered. Rotational invariance is broken by the same amount. This clearly indicates that the collinear approach should not be used, as the full treatment is easily implemented and does not introduce much more computational effort. © 2002 Wiley Periodicals, Inc. J Comput Chem 23: 779,785, 2002 [source]

Modelling the energy dependencies of X-ray quasi-periodic oscillations in accreting compact objects

Piotr T.
ABSTRACT We have constructed models of the quasi-periodic variability of X-ray emission from accreting compact objects. Assuming a general scenario of a propagation model of variability, with inverse Compton upscattering as the emission mechanism, we have considered a number of cases for the periodic modulation: modulation of the plasma heating rate, cooling rate by external soft photons and the amplitude of the reprocessed component. We have computed various observational characteristics which can be compared to good quality data. These include Fourier-frequency resolved spectra and the results of cross-correlation analysis between light curves at different energies. Each model of modulation predicts specific observational signatures, which help in identifying the physical processes driving quasi-periodic oscillations emission in accreting sources. [source]

Effects of Different Doses of Low Power Continuous Wave He,Ne Laser Radiation on Some Seed Thermodynamic and Germination Parameters, and Potential Enzymes Involved in Seed Germination of Sunflower (Helianthus annuus L.)

Rashida Perveen
In this study, water-soaked seeds of sunflower were exposed to He,Ne laser irradiation of different energies to determine whether or not He,Ne laser irradiation caused changes to seed thermodynamic and germination parameters as well as effects on the activities of germination enzymes. The experiment comprised four energy levels: 0 (control), 100, 300 and 500 mJ of laser energy and each treatment replicated four times arranged in a completely randomized design. The experimentation was performed under the greenhouse conditions in the net-house of the Department of Botany, University of Agriculture, Faisalabad. The seed thermodynamic parameters were calculated according to seed germination thermograms determined with a calorimeter at 25.8°C for 72 h. Various thermodynamic parameters of seed (,H, (,S)e, (,S)c, (,S)e/,t and (,S)c/,t) were affected significantly due to presowing laser treatment. Significant changes in seed germination parameters and enzyme activities were observed in seeds treated with He,Ne laser. The He,Ne laser seed treatment resulted in increased activities of amylase and protease. These results indicate that the low power continuous wave He,Ne laser light seed treatment has considerable biological effects on seed metabolism. This seed treatment technique can be potentially employed to enhance agricultural productivity. [source]

On the use of breakdown graphs combined with energy-dependent mass spectrometry to provide a complete picture of fragmentation processes

Colin P. G. Butcher
Both breakdown graphs and energy-dependent (ED) maps provide a means of visually representing the fragmentation processes resulting from collision-induced dissociation at different energies. The two presentation methods may be combined for a complete picture of the appearance, disappearance and maximum abundance collision potentials of each of the ions involved in the fragmentation process. A demonstration of this approach is presented using two very different classes of compound, an amino acid and a transition metal carbonyl cluster. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Nonlinear optical properties of poly-ortho-toluidine films implantated by N+ ions with different energy

Yan Shaolin
This article reports experimental work on the effect of N+ ion implantation on third-order nonlinear optical properties of POT films. Using K2Cr2O7 as oxidizing agent, poly- ortho -toluidine (POT) was synthesized in 1 M hydrochloric. The POT films were prepared by spin-coating method and then implantated by N+ ions (15,30 KeV) at a dose 1.9 × 1016 ions/cm2. The films were characterized by FT-IR spectroscopy, visible spectroscopy and SEM, their third-order nonlinear optical susceptibility (,(3)) were also examined by a degenerate four-wave mixing (DFWM) system at 532nm. Compared to pristine POT films, the optical band gap obtained from visible spectra decreased from 3.58 to 3.48 eV when the energy was 30 KeV. Also, The ,(3) value of implantated POT films increased from 3.31 × 10,10 esu to 4.04 × 10,9 esu when the implantated energy was 25 KeV. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source]