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 Nanostructured materials (2)
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Articles 1  11 of 11
FullText Articles in Physics
Transmission Electron Goniometry And Its Relation To Electron Tomography For Materials Science Apoplications, Peter Moeck, P. Fraundorf
Transmission Electron Goniometry And Its Relation To Electron Tomography For Materials Science Apoplications, Peter Moeck, P. Fraundorf
Physics Faculty Publications and Presentations
Aspects of transmission electron goniometry are discussed. Combined with high resolution phase contrast transmission electron microscopy (HRTEM) and atomic resolution scanning TEM (STEM) in the atomic number contrast (ZSTEM) or the phase contrast bright field mode, transmission electron goniometry offers the opportunity to develop dedicated methods for the crystallographic characterization of nanocrystals in three dimensions. The relationship between transmission electron goniometry and electron tomography for materials science applications is briefly discussed. Internet based java applets that facilitate the application of transmission electron goniometry for cubic crystals with calibrated tiltrotation and doubletilt specimen holders/goniometers are mentioned. The so called cubicminimalistic ...
A Transmission Electron Microscope For Lecture Demonstrations, J. A. Panitz, Gertrude Rempfer
A Transmission Electron Microscope For Lecture Demonstrations, J. A. Panitz, Gertrude Rempfer
Physics Faculty Publications and Presentations
A simple transmission electron microscope (TEM) suitable for lecture demonstrations is described. In this TEM electrons are created in a glow discharge between two parallel electrodes in air at a reduced pressure. The electrons are collimated by a small hole in theanode, focused by a solenoid that acts as an electromagnetic lens, and imaged on a thin layer of phosphor deposited inside an Erlenmeyer flask. An image of a biological sample placed between the source and the lens can be magnified about 20 times. The microscope uses inexpensive components that can be quickly assembled during a demonstration. The TEMprovides a ...
Relativistic Corrections To A Generalized Sum Rule, P.T. Leung, H. Sinky
Relativistic Corrections To A Generalized Sum Rule, P.T. Leung, H. Sinky
Physics Faculty Publications and Presentations
Relativistic corrections to a previously established generalized sum rule are obtained using the FoldyWouthysen transformation. This sum rule derived previously by Wang [Phys. Rev. A 60, 262 (1999)] for a nonrelativistic system contains both the wellknown ThomasReicheKuhn and Bethe sum rules, for which relativistic corrections have been obtained in the literature. Our results for the generalized formula will be applied to recover several results obtained previously in the literature, as well as to another sum rule whose relativistic corrections will be obtained.
TwoPhoton Spectroscopy Of Rubidium Using A GratingFeedback Diode Laser, Abraham J. Olson, Evan J. Carlson, Shannon K. Mayer
TwoPhoton Spectroscopy Of Rubidium Using A GratingFeedback Diode Laser, Abraham J. Olson, Evan J. Carlson, Shannon K. Mayer
Physics Faculty Publications and Presentations
We describe an experiment for investigating the 5S_{1/2}→5D_{5/2} twophoton transition in rubidium using a single gratingfeedback diode laser operating at 778.1nm (385 THz). Continuous tuning of the laser frequency over 4GHz allows for the clear resolution of the Dopplerfree spectral features and allows accurate measurement of the hyperfine groundstate splitting. A direct comparison between Dopplerbroadened and Dopplerfree spectral features is possible because both are distinctly evident in the twophoton spectra. By independently modifying the polarization state of the two laser fields, the impact of electric dipole selection rules on the twophoton transition spectra is ...
Nonlocal Effects On Optical And Molecular Interactions With Metallic Nanoshells, P.T. Leung, Railing Chang
Nonlocal Effects On Optical And Molecular Interactions With Metallic Nanoshells, P.T. Leung, Railing Chang
Physics Faculty Publications and Presentations
Theoretical studies of the optical response of metallic nanoshells have been carried out, where quantum effects are partially accounted for through the application of a nonlocal response model for shells of mesoscopic dimensions. Both far field and near field interactions are considered, with the incident source being a plane wave and an emitting molecular dipole, respectively. It is found that these nonlocal effects can lead to significant deviations from macroscopic electrodynamic theory, for shells of ultrasmall dimensions (<10 >nm) or ultrathin thickness (~1 nm), and are particularly significant for processes involving higher multipolar responses of the nanoshells. It is further concluded ...
SimilarityBased Constitutive Relations For Local Mass Fluxes In Incompressible Mixing Layers, John D. Ramshaw
SimilarityBased Constitutive Relations For Local Mass Fluxes In Incompressible Mixing Layers, John D. Ramshaw
Physics Faculty Publications and Presentations
The local concentrations of the two fluids within a mixing layer produced by an interfacial instability are determined by their individual continuity equations. Solution of these equations requires constitutive relations for the local mass fluxes of the two fluids. We derive explicit analytical expressions for these fluxes in planar incompressible mixing layers characterized by a single integral length scale h(t), which is presumed to be provided by a suitable mix or turbulence model. Elementary scaling arguments imply that in mixing layers of this type, the mean volume fraction profile α(x,t) depends on x and t only through ...
Quantum Phase Transitions In The Transverse OneDimensional Ising Model With FourSpin Interactions, O. F. De Alcantara Bonfim, J. Florencio
Quantum Phase Transitions In The Transverse OneDimensional Ising Model With FourSpin Interactions, O. F. De Alcantara Bonfim, J. Florencio
Physics Faculty Publications and Presentations
In this work we investigate the quantum phase transitions at zero temperature of the onedimensional transverse Ising model with an extra term containing fourspin interactions. The competition between the energy couplings of the model leads to an interesting zerotemperature phase diagram. We use a modified Lanczos method to determine the ground state and the first excited state energies of the system, with sizes of up to 20 spins. We apply finite size scaling to the energy gap to obtain the boundary region where ferromagnetic to paramagnetic transition takes place. We also find the critical exponent associated with the correlation length ...
Exact And Approximate Energy Spectrum For The Finite Square Well And Related Potentials, O. F. De Alcantara Bonfim, David J. Griffiths
Exact And Approximate Energy Spectrum For The Finite Square Well And Related Potentials, O. F. De Alcantara Bonfim, David J. Griffiths
Physics Faculty Publications and Presentations
We investigate the problem of a quantum particle in a onedimensional finite square well. In the standard approach the allowed energies are determined implicitly as the solutions to a transcendental equation. We obtain the spectrum analytically as the solution to a pair of parametric equations and algebraically using a remarkably accurate approximation to the cosine function. The approach is also applied to a variety of other quantum wells.
Lattice Fringe Fingerprinting In Two Dimensions With Database Support, Peter Moeck, B. Seipel, R. Bjorge, P. Fraundorf
Lattice Fringe Fingerprinting In Two Dimensions With Database Support, Peter Moeck, B. Seipel, R. Bjorge, P. Fraundorf
Physics Faculty Publications and Presentations
A brief introduction to lattice fringe fingerprinting in two dimensions (2D) with database support is given. The method is employed for the identification of the crystal phase of a small ensemble of nanocrystals. The enhanced viability of this method in aberrationcorrected transmission electron microscopes (TEMs) and scanning TEMs (STEMs) is also illustrated.
ImageBased Nanocrystallography With Online Database Support, Peter Moeck, Ján Zahornadsky, Boris Dusek
ImageBased Nanocrystallography With Online Database Support, Peter Moeck, Ján Zahornadsky, Boris Dusek
Physics Faculty Publications and Presentations
The crystallographic phase and morphology of many materials change with the crystal size so that new needs arise to determine the crystallography of nanocrystals. Direct space highresolution phasecontrast transmission electron microscopy (HRTEM) and atomic resolution scanning TEM (STEM) when combined with tools for imagebased nanocrystallography in two (2D) and three (3D) dimensions possess the capacity to meet these needs. After a concise discussion of latticefringe visibility spheres and maps, this paper discusses latticefringe fingerprinting in 2D and tilt protocol applications. Online database developments at Portland State University (PSU) that support imagebased nanocrystallography are also mentioned.
Probing Nanoscale Ferroelectricity By Ultraviolet Raman Spectroscopy, Dmitri Tenne, A. Bruchhausen, N. D. LanzillottiKimura, A. Fainstein, R. S. Katiyar, A. Cantarero, A. Soukiassian
Probing Nanoscale Ferroelectricity By Ultraviolet Raman Spectroscopy, Dmitri Tenne, A. Bruchhausen, N. D. LanzillottiKimura, A. Fainstein, R. S. Katiyar, A. Cantarero, A. Soukiassian
Physics Faculty Publications and Presentations
We demonstrate that ultraviolet Raman spectroscopy is an effective technique to measure the transition temperature, T_{c}, accurately in ferroelectric ultrathin films and superlattices. We show that oneunitcell thick BaTiO_{3} layers in BaTiO_{3}/SrTiO_{3} superlattices are not only ferroelectric (Tc as high as 250 K), but also polarize the quantum paraelectric SrTiO_{3} layers adjacent to them. T_{c} was tuned by ~ 500 K by varying the thicknesses of BaTiO_{3} and SrTiO_{3} layers, revealing the essential roles of electrical and mechanical boundary conditions for nanoscale ferroelectricity.