scholarly journals (e,2e) Studies of Atoms ? Some Recent Developments

1990 ◽  
Vol 43 (5) ◽  
pp. 543 ◽  
Author(s):  
Erich Weigold
Keyword(s):  
Momentum Density ◽  
Strong Correlations ◽  
Many Body ◽  
Scattered Electron ◽  
Initial State ◽  
Final State ◽  
Hartree Fock ◽  
Resolution Electron ◽  
Electron Momentum Spectroscopy ◽  
Recent Developments

Some recent work on (e,2e) collisions in atoms is reported. The first (e,2e) results on an excited target and also on an oriented target are discussed. Sodium atoms are pumped to the m/ = +1 state of the excited 3p state by 0"+ light from a laser. The (e,2e) measurements are then performed on this excited state. The results are in excellent agreement with the momentum density profile given by the 3p(m/ = 1) Hartree-Fock wavefunction. High resolution electron momentum spectroscopy measurements are reported for argon. The first momentum profiles for excited Ar ion states belonging to the 2po and 20e manifolds are obtained. The latter are entirely due to initial state correlations. Comparison is made with several many-body calculations. The importance of core quadrupole (10) excitations is demonstrated. Although the 2se manifold is dominated by final state correlations, the momentum profile to the 4s 2S ion state in the 2Se manifold also shows the influenee of initial state correlation effects. The third series of measurements examines correlations in the autoionising region of helium, encompassing the (2s2)1 S, (2s2p)3p, (2p2)! 0 and (2s2p)! P resonances, at 100, 200 and 400 eV incident electron energies. Measurements, with an energy resolution of 150 meV, were taken at a number of scattered electron angles over an extended range of ejected electron angles, encompassing both the binary and recoil regions. The data show very strong correlations between the resonance amplitudes and the direct ionisation amplitudes.

Recent Advances in Electron Momentum Spectroscopy

1993 ◽  
Vol 48 (1-2) ◽  
pp. 371-389
Author(s):  
Erich Weigold
Keyword(s):  
Excited State ◽  
Valence Electron ◽  
Condensed Matter ◽  
Momentum Density ◽  
Initial State ◽  
Electron Momentum ◽  
Hartree Fock ◽  
Electron Momentum Spectroscopy ◽  
Momentum Distributions ◽  
D Wave

Abstract The flexibility of the (e, 2e) technique or "electron momentum spectroscopy" (EMS) in obtaining information on the electronic structure of atoms, molecules, and solids is demonstrated. High-resolution EMS measurements for argon, including the first measurements of momentum profiles belonging to the 2P0 and 2De -manifolds, are used to demonstrate the technique for atomic targets. The d-wave transitions in argon are entirely due to initial-state correlations. The first (e, 2e) measurements on an excited target, and also on an oriented target, are discussed. Sodium atoms are pumped to the ml = +1 state of the excited 3p-state by σ+ -light from a laser. The (e, 2e) measurements on this excited state are in excellent agreement with the momentum density given by the 3p (ml - 1) Hartree-Fock wavefunction. The recent measurements of the valence-electron momentum distributions for ethyne, as well as some earlier results for water, are used as an example of the application of EMS to the study of molecules. The application of the EMS technique to measure spectral momentum densities in condensed-matter targets is demonstrated by some recent results on amorphous carbon.

The Spectral Momentum Density of Aluminium, Copper and Gold Measured by Electron Momentum Spectroscopy

2001 ◽  
Vol 215 (10) ◽  
Author(s):  
A. S. Kheifets ◽  
M. Vos ◽  
E. Weigold
Keyword(s):  
Electron Correlation ◽  
High Energy ◽  
Momentum Density ◽  
Correlation Effects ◽  
Many Body ◽  
Electron Momentum ◽  
Aluminium Copper ◽  
Electron Momentum Spectroscopy ◽  
Electron Correlation Effects ◽  
Good Agreement

Electron momentum spectroscopy (EMS) gives direct information of the full energy-resolved electron momentum densities of occupied states (bands) in solids – single crystal, polycrystalline or amorphous. Here we present data from a new high energy EMS spectrometer using 50 keV incident and 25 keV outgoing electrons, on polycrystalline specimens of aluminium, copper and gold. The spectral momentum densities show very significant electron-electron correlation effects which are in good agreement with many-body Green´s function calculations.

Recent developments in automated Transmission Electron MI

1989 ◽  
Vol 47 ◽  
pp. 46-47
Author(s):  
W.J. de Ruijter ◽  
P. Rez ◽  
David J. Smith
Keyword(s):  
Image Analysis ◽  
Computer Image ◽  
Lens Design ◽  
Computer Image Analysis ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Recent Developments ◽  
On Line ◽  
Routine Procedures ◽  
Near Future

There is growing interest in the on-line use of computers in high-resolution electron n which should reduce the demands on highly skilled operators and thereby extend the r of the technique. An on-line computer could obviously perform routine procedures hand, or else facilitate automation of various restoration, reconstruction and enhan These techniques are slow and cumbersome at present because of the need for cai micrographs and off-line processing. In low resolution microscopy (most biologic; primary incentive for automation and computer image analysis is to create a instrument, with standard programmed procedures. In HREM (materials researc computer image analysis should lead to better utilization of the microscope. Instru (improved lens design and higher accelerating voltages) have improved the interpretab the level of atomic dimensions (approximately 1.6 Å) and instrumental resolutior should become feasible in the near future.

Quantitative high-resolution electron microscopy (HREM) of defects in ordered polymers

1996 ◽  
Vol 54 ◽  
pp. 166-167
Author(s):  
Patricia M. Wilson ◽  
David C. Martin
Keyword(s):  
Electron Microscopy ◽  
Electron Beam ◽  
High Resolution ◽  
Liquid Crystalline ◽  
High Resolution Electron Microscopy ◽  
Polymer Materials ◽  
Scattered Electron ◽  
Crystalline Polymers ◽  
Resolution Electron ◽  
Beam Damage

Efforts in our laboratory and elsewhere have established the utility of low dose high resolution electron microscopy (HREM) for imaging the microstructure of crystalline and liquid crystalline polymers. In a number of polymer systems, direct imaging of the lattice spacings by HREM has provided information about the size, shape, and relative orientation of ordered domains in these materials. However, because of the extent of disorder typical in many polymer microstructures, and because of the sensitivity of most polymer materials to electron beam damage, there have been few studies where the contrast observed in HREM images has been analyzed in a quantitative fashion.Here, we discuss two instances where quantitative information about HREM images has been used to provide new insight about the organization of crystalline polymers in the solid-state. In the first, we study the distortion of the polymer lattice planes near the core of an edge dislocation and compare these results to theories of dislocations in anisotropic and liquid crystalline solids. In the second, we investigate the variations in HREM contrast near the edge of wedge-shaped samples. The polymer used in this study was the diacetylene DCHD, which is stable to electron beam damage (Jc = 20 C/cm2) and highly crystalline. The instrument used in this work was a JEOL 4000 EX HRTEM with a beam blanidng device. More recently, the 4000 EX has been installed with instrumentation for dynamically recording scattered electron beam currents.

Shot-noise simulations of HREM images of polymer crystals

1989 ◽  
Vol 47 ◽  
pp. 342-343
Author(s):  
Philippe Pradère ◽  
Edwin L. Thomas
Keyword(s):  
Low Dose ◽  
Molecular Level ◽  
High Resolution Electron Microscopy ◽  
Crystal Defects ◽  
Inorganic Materials ◽  
Photographic Emulsion ◽  
Polymer Crystals ◽  
Resolution Electron ◽  
Recent Developments ◽  
Lattice Images

High Resolution Electron Microscopy (HREM) is a very powerful technique for the study of crystal defects at the molecular level. Unfortunately polymer crystals are beam sensitive and are destroyed almost instantly under the typical HREM imaging conditions used for inorganic materials. Recent developments of low dose imaging at low magnification have nevertheless permitted the attainment of lattice images of very radiation sensitive polymers such as poly-4-methylpentene-1 and enabled molecular level studies of crystal defects in somewhat more resistant ones such as polyparaxylylene (PPX) [2].With low dose conditions the images obtained are very noisy. Noise arises from the support film, photographic emulsion granularity and in particular, the statistical distribution of electrons at the typical doses of only few electrons per unit resolution area. Figure 1 shows the shapes of electron distribution, according to the Poisson formula :

scholarly journals Dual subtractions

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Renato Maria Prisco ◽  
Francesco Tramontano
Keyword(s):  
Field Theory ◽  
Quantum Field ◽  
Matrix Elements ◽  
Leading Order ◽  
Initial State ◽  
Final State ◽  
Dual Representation ◽  
Subtraction Scheme ◽  
Theoretical Predictions ◽  
Perturbative Quantum

Abstract We propose a novel local subtraction scheme for the computation of Next-to-Leading Order contributions to theoretical predictions for scattering processes in perturbative Quantum Field Theory. With respect to well known schemes proposed since many years that build upon the analysis of the real radiation matrix elements, our construction starts from the loop diagrams and exploits their dual representation. Our scheme implements exact phase space factorization, handles final state as well as initial state singularities and is suitable for both massless and massive particles.

scholarly journals Undecidability in quantum thermalization

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Naoto Shiraishi ◽  
Keiji Matsumoto
Keyword(s):  
Turing Machine ◽  
Thermal Equilibrium ◽  
General Theorem ◽  
Nearest Neighbour ◽  
Many Body ◽  
Initial State ◽  
One Dimensional ◽  
Universal Turing Machine ◽  
Many Body Systems ◽  
Neighbour Interaction

AbstractThe investigation of thermalization in isolated quantum many-body systems has a long history, dating back to the time of developing statistical mechanics. Most quantum many-body systems in nature are considered to thermalize, while some never achieve thermal equilibrium. The central problem is to clarify whether a given system thermalizes, which has been addressed previously, but not resolved. Here, we show that this problem is undecidable. The resulting undecidability even applies when the system is restricted to one-dimensional shift-invariant systems with nearest-neighbour interaction, and the initial state is a fixed product state. We construct a family of Hamiltonians encoding dynamics of a reversible universal Turing machine, where the fate of a relaxation process changes considerably depending on whether the Turing machine halts. Our result indicates that there is no general theorem, algorithm, or systematic procedure determining the presence or absence of thermalization in any given Hamiltonian.

scholarly journals Using Matrix-Product States for Open Quantum Many-Body Systems: Efficient Algorithms for Markovian and Non-Markovian Time-Evolution

Entropy ◽  
2020 ◽  
Vol 22 (9) ◽  
pp. 984
Author(s):  
Regina Finsterhölzl ◽  
Manuel Katzer ◽  
Andreas Knorr ◽  
Alexander Carmele
Keyword(s):  
Time Evolution ◽  
Nearest Neighbor ◽  
Matrix Product ◽  
Body System ◽  
Many Body ◽  
Initial State ◽  
Matrix Product States ◽  
Open Quantum ◽  
Many Body Systems ◽  
The Many

This paper presents an efficient algorithm for the time evolution of open quantum many-body systems using matrix-product states (MPS) proposing a convenient structure of the MPS-architecture, which exploits the initial state of system and reservoir. By doing so, numerically expensive re-ordering protocols are circumvented. It is applicable to systems with a Markovian type of interaction, where only the present state of the reservoir needs to be taken into account. Its adaption to a non-Markovian type of interaction between the many-body system and the reservoir is demonstrated, where the information backflow from the reservoir needs to be included in the computation. Also, the derivation of the basis in the quantum stochastic Schrödinger picture is shown. As a paradigmatic model, the Heisenberg spin chain with nearest-neighbor interaction is used. It is demonstrated that the algorithm allows for the access of large systems sizes. As an example for a non-Markovian type of interaction, the generation of highly unusual steady states in the many-body system with coherent feedback control is demonstrated for a chain length of N=30.

scholarly journals THE METHOD OF INCREMENTS — A WAVEFUNCTION-BASED AB-INITIO CORRELATION METHOD FOR SOLIDS

2007 ◽  
Vol 21 (13n14) ◽  
pp. 2204-2214 ◽  
Author(s):  
BEATE PAULUS
Keyword(s):  
Experimental Data ◽  
Ab Initio ◽  
Ground State ◽  
Infinite System ◽  
Correlation Energy ◽  
Correlation Method ◽  
Many Body ◽  
Hartree Fock ◽  
The Many ◽  
Good Agreement

The method of increments is a wavefunction-based ab initio correlation method for solids, which explicitly calculates the many-body wavefunction of the system. After a Hartree-Fock treatment of the infinite system the correlation energy of the solid is expanded in terms of localised orbitals or of a group of localised orbitals. The method of increments has been applied to a great variety of materials with a band gap, but in this paper the extension to metals is described. The application to solid mercury is presented, where we achieve very good agreement of the calculated ground-state properties with the experimental data.

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