Showing papers on "Free electron model published in 1972"
TL;DR: In this article, the angular correlations between scattered and ejected electrons were measured for electron impact ionization of helium for the impact energy E0=256.5 eV, and the angular distribution of the corresponding slow electrons consists of two maxima (approximately at -60 degrees and +120 degrees ) in opposite directions and zero in between.
Abstract: Measurements of angular correlations between scattered and ejected electrons are presented for electron impact ionization of helium for the impact energy E0=256.5 eV. The two outgoing electrons are measured in coincidence. The fast electrons are detected at fixed angles (
49 citations
TL;DR: In this article, the x-ray structure amplitudes for the 27 lowest-angle Bragg reflections of beryllium metal have been measured on an absolute scale and compared with those predicted both by the free atom Hartree-Foch wave functions and by a free electron orthogonalized plane wave model.
Abstract: The x-ray structure amplitudes for the 27 lowest-angle Bragg reflections of beryllium metal have been measured on an absolute scale. These can be used to deduce the charge density. The measured structure amplitudes are compared with those predicted both by the free atom Hartree-Foch wave functions and by a free electron orthogonalized plane wave model. For both models the predicted value for the lowest angle reflection is close to that observed, but the structure amplitudes of subsequent reflections given by the models are significantly greater than those observed. To account for these discrepancies a model of beryllium involving 2p-like tight binding functions is proposed.
45 citations
TL;DR: The amorphous metals Bi, Ga, Sn and Pb are obtained by quenched condensation and their Hall effect is measured and compared with the model of free electrons as mentioned in this paper.
Abstract: The amorphous metals Bi, Ga, Sn and Pb are obtained by quenched condensation. Their Hall effect is measured and compared with the model of free electrons. For Ga and Sn we find a good agreement with the free electron model. However, the Hall coefficient of Bi and Pb is only half as large as the theoretical value. This is particularly surprising because the corresponding liquids agree well with the free electron model and the amorphous state closely resembles the liquid. A trace effect of band structure may be responsible for the deviation.
28 citations
TL;DR: In this paper, an analysis of the equilibrium between bound and free electrons identifies important features of the binding which have not previously been considered, which are not previously considered in the literature.
Abstract: Methods have been developed for depositing electrons on the surface of liquid helium, either from the gas side or from the liquid side. In a suitable applied electric field they escape from the surface into the gas and the rate of escape has been measured. Electrons inside the surface escape by a thermally activated process. Those outside the surface escape much more rapidly by what appears to be a tunneling process. Analysis of the equilibrium between bound and free electrons identifies important features of the binding which have not previously been considered.
28 citations
Patent•
24 May 1972
TL;DR: In this article, population inversion is achieved between a number of these metastable energy states and states of lower energy, negative absorption being then produced for the transition which couples the metastable states with said states of higher energy.
Abstract: A plasma is formed from a material in which the ions possess discrete metastable energy states interacting with the energy states of the continuum which are populated by the free electrons of the plasma. Population inversion is achieved between a number of these metastable states and states of lower energy, negative absorption being then produced for the transition which couples the metastable states with said states of lower energy.
25 citations
TL;DR: In this paper, an analytical expression for the damping rate of a long-wavelength plasma wave in terms of the optical constants of the medium which supports the wave was given.
22 citations
TL;DR: In this article, the spectral structure due to the conduction band is discussed with reference to simple two band models with the relativistic effects accounted for in a qualitative manner, and new structure is predicted in the absorption spectra of binary solid solutions of free electron like metals.
Abstract: UV photoemission spectra from clean, Cs and Cs + O2 coated Ag are reported. The results, which include temperature and angular dependence, are discussed in terms of the Ag band structure. The spectral structure due to the conduction band is discussed with reference to simple two band models with the relativistic effects accounted for in a qualitative manner. New structure is predicted in the absorption spectra of binary solid solutions of free electron like metals.
21 citations
TL;DR: In this paper, a model of the enhancement of lattice tails in the positron annihilation due to electron-positron correlations is presented, where a weak lattice is handled in a Green's function technique by a modified ladder approximation which includes the lattice to lowest order as an electron-lattice interaction.
20 citations
TL;DR: In this paper, photoionization cross sections for all levels belonging to the configurations of atoms and ions of aluminum, silicon, and argon have been calculated using Hartree-Fock bound-electron wave functions and close-coupling approximation free-electric wave functions.
Abstract: Photoionization cross sections for all levels belonging to the configurations of atoms and ions of aluminum, silicon, and argon have been calculated using Hartree-Fock bound-electron wave functions and close-coupling approximation free-electron wave functions. The results are presented in the form of a computationally convenient interpolation formula and should find wide astrophysical application.
19 citations
TL;DR: In this paper, the effect of adsorbed ordered and disordered overlayers on the specular reflectivity, I 00, of low-energy electrons normally incident on Ni(001) has been investigated.
19 citations
TL;DR: In this article, a theory of tunneling and field emission of electrons from such surface states is developed, which can occur not only in energy gaps caused by Bragg reflections at Brillouin zone faces but also in spin-orbit split gaps and hybridization gaps within the zone.
Abstract: Solids with electron band structures given by a simple analytic function of wavenumber (E∼k2 for free electron bands; E∼k for tightbinding bands) possess localized electron states at their surfaces which are easily treated within the complex k vector formalism developed especially by Heine and collaborators. These surface states, which will be called Cambridge surface states, can occur not only in energy gaps caused by Bragg reflections at Brillouin zone faces but also in spin-orbit split gaps and hybridization gaps within the zone. In this work a theory of tunneling and field emission of electrons from such surface states is developed. The field emission energy distribution from d-band metal surface states is calculated using Harrison’s d-band pseudopotential theory, and the results are favorably compared with experimental data. Since the existence conditions for Cambridge surface states depend crucially upon the boundary conditions at the surface, the act of measurement via a tunneling process can suffi...
TL;DR: In this paper, a flat maximum of electron density at centers of interstices is proposed as well as preferential occupancy of either octahedral or tetrahedral interstice.
Abstract: Application of the Hellmann-Feynman Theorem to Metals has led to an interstitial-electron model in which there is some localization of itinerant electron density in octahedral or tetrahedral interstices of close-packed metal ion cores. A flat maximum of electron density at centers of interstices is proposed as well as preferential occupancy of either octahedral or tetrahedral interstices. Such occupancy is rather precisely determined by the requirements of minimum electron-electron repulsion and of opposite spins for electrons in adjacent interstices. Writing the interstitial-electron structure of a metal in terms of interstice occupancy thus includes electron correlation effects. The interstitial-electron structures are instantaneous pictures of electron density which are representative of the highly dynamic situation of electrons in metals. The model leads to localization of d-electrons on the metal-ion core when interstices are fully occupied by itinerant electrons, i.e. at M6+. The presence of vacant ...
IBM1
TL;DR: In this paper, the authors show that a simple metal description of the electronic states in compounds of the LaX 3 type is not tenable and perform energy band calculations using a simple model potential and obtain the density of states using a version of the Gilat-Raubenheimer k -space integration scheme due to Janak.
TL;DR: In this paper, it was shown that there is a QSE solution of the simple model exactly at a band edge if and only if the one Floquet solution at that band edge vanishes at the surface.
Abstract: It is shown that there is a QSE solution of the simple model exactly at a band edge if and only if the one Floquet solution at that band edge vanishes at the surface. This condition is applied to the free electron model, the nearly free electron model, the Kronig-Penney delta well model, and the tight binding model. The solutions near a band edge are also studied, and found to have simple approximate forms, namely u0(x) cos pi nx/L or u0(x) sin pi nx/L according as there is or is not a solution exactly at the band edge. The importance of the solutions at and near the band edges for spectroscopic studies of the QSE is pointed out.
TL;DR: In this article, the valence charge density associated with the nearly free electron dielectric matrix of silicon is computed and the part arising from the off-diagonal dielectrics elements is shown to contain the effects of covalency, and displays the piling up of bonding charge between the ions.
Abstract: The valence charge density associated with the nearly free electron dielectric matrix of silicon is computed. The part arising from the off-diagonal dielectric elements is shown to contain the effects of covalency, and displays the piling up of bonding charge between the ions.
TL;DR: In this article, a model for the Gunn-effect-domain dynamics in the presence of traps is studied, both analytically and by computer simulation, and it is found that the electron-dipole domain is coupled to an ion-dipsole domain which can move only by charging and discharging ions and which slows down the overall domain speed by a factor equal to the ratio of untrapped free electrons to ionized donors.
Abstract: A model for the Gunn‐effect‐domain dynamics in the presence of trapping is studied, both analytically and by computer simulation. The model assumes that in addition to the conventional donors there is a much larger density of traps present which are neutral when empty. The capture‐ and release‐time constants are assumed to be field independent. It is found that the electron‐dipole domain is coupled to an ion‐dipole domain which can move only by charging and discharging ions and which slows down the overall domain speed by a factor equal to the ratio of untrapped free electrons to ionized donors. The same factor also determines the fraction of the total domain voltage supported by the electron dipole; the remainder is supported by the ion dipole. For sufficiently strong trapping the net ion charge throughout part of the ion domain is actually negative, resembling an npn structure with a punched‐through traveling p‐type base.
TL;DR: In this paper, the intrinsic surface states in nearly free-electron metals are discussed and their energies are calculated in the two-band approximation for the band gaps at the faces or inside a three-dimensional Brillouin zone.
TL;DR: In this paper, the dispersion of the surface loss wave excited by incoming electrons in various semiconducting films was studied using the Drude-Lorentz dielectric constant model.
TL;DR: In this paper, the interaction of an intense, circularly polarized, electromagnetic wave of finite duration with a free electron is analyzed classically and the effects of radiative reaction and intensity gradients in smoothly varying pulses are treated relativistically.
Abstract: The interaction of an intense, circularly polarized, electromagnetic wave of finite duration with a free electron is analyzed classically. The effects of radiative reaction and intensity gradients in smoothly varying pulses are treated relativistically. It is shown that the effect of radiative reaction is to impart to the electron a final energy which depends only on the energy per unit area carried by the wave.
TL;DR: In this article, the authors studied the trap and detrapping of free electrons in high-purity silicon after irradiation with 14-MeV neutrons and developed a model which describes most of the results quantitatively and self-consistently, including dc characteristics.
Abstract: The trapping and detrapping of electrons is studied through measurements of space-charge-limited current in the temperature range of 77 to 293 K in high-purity silicon after irradiation with 14-MeV neutrons. A model is developed which describes most of the results quantitatively and self-consistently, including dc characteristics. Two distinct trap levels exist: the fast levels lie at 0.14 (plus or minus 0.005) eV below the conduction band, and the slow levels lie at 0.47 (plus or minus 0.01) eV below the conduction band. At 77 K, injected free electrons are initially captured by the fast 0.14-eV traps and then sink into the deep 0.47-eV traps, predominantly without being reemitted into the band. Above approximately 110 K, the detrapping rate from the shallow traps becomes so fast that the deep traps dominate. The results also offer a direct verification of the simple model of space-charge-limited current dominated by shallow and deep traps.
TL;DR: In this article, the total energy distribution (TED) of field emitted electrons has been measured for [012] direction of tungsten monocrystal in temperature region from 78 K to 950 K. The explanation of obtained results has been proposed, taking into account the electron scattering phenomena of electrons supplied to the surface during the emission.
TL;DR: In this article, an algebraic technique for the evaluation of the coefficients of a general transport equation for dynamically independent electrons in the presence of random impurities was developed. But this method readily yields, for arbitrarily strong single center potentials, these coefficients in powers of the density of the impurities.
TL;DR: In this paper, the Larmor frequency of free electrons in an electrostatic quadrupole trap with superimposed homogeneous magnetic field was measured via a measurement of the polarization change of the atomic beam.
TL;DR: In this paper, the effect of radiative reaction on the electron orbit is accounted for self-consistently, and expressions for the total scattering cross section, the angular and spectral distributions, and the polarization tensor of the scattered radiation are derived.
Abstract: The radiation from an electron driven by an intense circularly polarized electromagnetic wave of finite duration and smoothly varying intensity is analyzed. The effect of radiative reaction on the electron orbit is accounted for self-consistently. Expressions are derived for the total scattering cross section, the angular and spectral distributions, and the polarization tensor of the scattered radiation. The results are relativistically correct, and exhibit the dependence of the characteristics of the scattered radiation on the intensity profile of the incident radiation.
TL;DR: An exact microscopic formula for the transverse dynamical susceptibility is derived from the spin rotation invariance properties of the model in this article, where the same properties allow the definition on a microscopic basis of the effective magnon-magnon interaction.
Abstract: An exact microscopic formula for the transverse dynamical susceptibility is derived from the spin rotation invariance properties of the model. The same properties allow the definition on a microscopic basis of the effective magnon-magnon interaction. As a concrete application of the above general results we calculate the low-temperature behavior of the spin-wave energy due to magnon-magnon interaction in the long-wavelength limit. For Ni in the parabolic band approximation and strong ferromagnetism limit we haveC2(K)=8.3×10−5T5/2K2 meV.
TL;DR: In this article, a comparison of the emission spectra produced under photoexcitation and cathodo-excitation reveals a peak wavelength difference, interpreted in terms of a difference between the effective electron temperature of free electrons for the two modes of excitation.
Abstract: Comparison of the emission spectra produced under photoexcitation and cathodoexcitation reveals a peak wavelength difference. This is interpreted in terms of a difference between the effective electron temperature of free electrons for the two modes of excitation and leads to a brief discussion of possible complications in the interpretations of radiative recombination processes.
TL;DR: In this article, a model that takes into account the effect of the finite skin depth in a determination of the phonon-limited electronic mean free path (EMFP) by means of the radiofrequency-size-effect amplitude was proposed.
Abstract: A model is proposed which takes into account the effect of the finite skin depth in a determination of the phonon-limited electronic mean free path (EMFP) by means of the radiofrequency-size-effect amplitude. The model results in a temperature dependence of the inverse EMFP which obeys neither aTn nor anaT3+bT5 law, in general. Numerical examples show the pureT3 behavior usually expected is reasonable for small Fermi radii of curvature, but that more complicated behavior can be expected for Fermi surfaces having nearly free electron curvature. Existing data from the “lens” of Cd, obeying an apparentT5 law, are discussed in terms of the present model.
TL;DR: In this paper, the Li-free-free scaled absorption coefficient is calculated at the infrared threshold using the phase shifts for the elastic scattering of electrons by neutral lithium atoms, and contributions to the cross section for different values of the angular momentum of the free electron are investigated.
Abstract: The Li- free-free scaled absorption coefficient is calculated at the infrared threshold using the phase shifts for the elastic scattering of electrons by neutral lithium atoms. Contributions to the cross section for different values of the angular momentum of the free electron are investigated.