Topic
Free electron model
About: Free electron model is a research topic. Over the lifetime, 4678 publications have been published within this topic receiving 103535 citations.
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TL;DR: In this article, the authors used a scanning tunneling microscope (STM) to study the local properties of low-dimensional electrons and found that Fe adatoms strongly scatter the surface states and are good building blocks for constructing atomic-scale barriers to confine the surface state electrons.
Abstract: Electrons occupying surface states on the close-packed faces of noble metals form a two-dimensional (2-d) nearly free electron gas. Because this system is accessible to the scanning tunneling microscope (STM), it provides a unique opportunity to study the local properties of low-dimensional electrons. On Cu(111) we have observed standing wave patterns in the surface local density of states due to the quantum mechanical interference of surface state electrons scattering off of step edges and adsorbates. We find that Fe adatoms strongly scatter the surface state and, as a result, are good building blocks for constructing atomic-scale barriers (“quantum corrals”) to confine the surface state electrons. The barriers are constructed by individually positioning Fe adatoms using the tip of a cold (4 K) STM. Tunneling spectroscopy performed inside of the corrals reveals discrete resonances, consistent with size quantization. A more quantitative understanding is obtained by accounting for the multiple scattering of surface state electrons with the corrals’ constituent adatoms. This scattering is characterized by a complex phase shift which can be extracted from the electronic density pattern inside a quantum corral.
45 citations
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TL;DR: In this article, the intrinsic emittance and transverse momentum distributions obtained from a metal photocathode near and below the photo-emission threshold were analyzed and shown to be limited by the lattice temperature of the cathode.
Abstract: Measurements of the intrinsic emittance and transverse momentum distributions obtained from a metal (antimony thin film) photocathode near and below the photoemission threshold are presented Measurements show that the intrinsic emittance is limited by the lattice temperature of the cathode as the incident photon energy approaches the photoemission threshold A theoretical model to calculate the transverse momentum distributions near this photoemission threshold is presented An excellent match between the experimental measurements and the theoretical calculations is demonstrated These measurements are relevant to low emittance electron sources for Free Electron Lasers and Ultrafast Electron Diffraction experiments
45 citations
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TL;DR: In this paper, the Boltzmann equation for free electrons in a low-temperature plasma is analyzed and it is shown how this equation can approximately be solved for electrons under a HF field of frequency ω (including the particular case of a dc field, which corresponds to the limit ω = 0).
Abstract: In the first part of this paper we briefly review some basic concepts of kinetic theory. The concept of the velocity distribution function is first introduced and its meaning is discussed. Then, the Boltzmann equation is presented on physical grounds and it is shown that the fluid equations are its moments. In the second part, the Boltzmann equation for free electrons in a low-temperature plasma is analysed. It is shown how this equation can approximately be solved for electrons under a HF field of frequency ω (including the particular case of a dc field, which corresponds to the limit ω = 0) by using a first-order double expansion in spherical harmonics in velocity space and a Fourier series in time. The electron transport parameters, particle balance and energy balance are analysed from a general point of view. Finally, an application to argon and nitrogen is given. The effects of changes in the field frequency on the electron energy distribution function, transport parameters and power balance are discussed. The importance of the coupling between the electron and the vibrational kinetics in N2 is emphasized.
45 citations
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TL;DR: In this paper, angle-resolved two-photon photoemission was used to measure changes in the binding energy and dispersion of image states for a Xe monolayer on the Ag(111) surface.
45 citations
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TL;DR: In this article, the number of free electrons in a sample decreased with increasing pulse off time, assuming that free radicals are generated only during the pulse on time and the reaction of a free radical with a gas species.
Abstract: Pulsed-rf excitation of hexafluoropropylene oxide has been used to deposit poly(tetrafluoroethylene)-like thin films. Films were deposited at pulse rates of 10/20, 10/50, 10/200, and 10/400 ms on/ms off and analyzed using electron spin resonance spectroscopy (ESR). All four films produced similar broad ESR spectra, with an average width at maximum slope of ∼60 G and a g value of 2.0045. The number of free electrons in a sample decreased with increasing pulse off time. This behavior can be modeled by the reaction of a free radical with a gas species, assuming that free radicals are generated only during the pulse on time.
45 citations