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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: A model describing the free-electron generation in transparent solids under high-intensity laser irradiation that follows the nonstationary energy distribution of electrons on ultrashort time scales as well as the transition to the asymptotic avalanche regime for longer irradiations.
Abstract: We develop a model describing the free-electron generation in transparent solids under high-intensity laser irradiation. The multiple rate equation model unifies key points of detailed kinetic approaches and simple rate equations to a widely applicable description, valid on a broad range of time scales. It follows the nonstationary energy distribution of electrons on ultrashort time scales as well as the transition to the asymptotic avalanche regime for longer irradiations. The role of photoionization and impact ionization is clarified in dependence on laser pulse duration and intensity.
272 citations
TL;DR: In this paper, ground states are divided into ground states and shallow trapping states, and the major recombination traffic passes through the ground states, where the discrete states in the forbidden zone are separated into ground and shallow states.
Abstract: The discrete states in the forbidden zone are divided into ground states and shallow trapping states. The major recombination traffic passes through the ground states. The shallow trapping states cause the observed decay time of free carrier concentrations to exceed the lifetime of a free carrier in the conduction (or valence) band. At low rates of excitation (free carrier concentrations less than ground state concentrations) the electron lifetime and hole lifetime are independent and, in general, significantly different. At high rates of excitation the free electron and hole lifetimes are equal. For an insulator having one class of ground states (a class being defined by the capture cross sections for electrons and holes) the high-light lifetime is bracketed by the two low-light lifetimes.The behavior of a model having one class of ground states can be described relatively simply and quantitatively. The behavior of a model having more than one class of ground states becomes sufficiently complex that only special cases can be treated easily. More than one class of ground states, however, is required to account for infrared quenching, "superlinearity" and the ability of added ground states to reduce the rate of recombination. These phenomena involve a redistribution of electrons and holes amongst the classes of ground states. Such redistributions can give some meaning to the phrases: "filling of traps" or "saturation of centers."The recombination behavior of a semiconductor is significantly different from that of an insulator. For example, superlinearity can occur in a semiconductor having only one class of ground states. Also, the photocurrents in a semiconductor can be intrinsically more noisy than the photocurrents in an insulator.
271 citations
TL;DR: In this article, the authors measured the reflectance as a function of wavelength in the visible spectrum finding values as high as 0.90 from the metallic hydrogen at a pressure of 495 GPa.
Abstract: We have studied solid hydrogen under pressure at low temperatures. With increasing pressure we observe changes in the sample, going from transparent, to black, to a reflective metal, the latter studied at a pressure of 495 GPa. We have measured the reflectance as a function of wavelength in the visible spectrum finding values as high as 0.90 from the metallic hydrogen. We have fit the reflectance using a Drude free electron model to determine the plasma frequency of 30.1 eV at T= 5.5 K, with a corresponding electron carrier density of 6.7x1023 particles/cm3, consistent with theoretical estimates. The properties are those of a metal. Solid metallic hydrogen has been produced in the laboratory.
268 citations
TL;DR: In this article, the nonlinear wave equation and self-consistent pendulum equation are generalized to describe free-electron laser operation in higher harmonics; this can significantly extend their tunable range to shorter wavelengths.
Abstract: The nonlinear wave equation and self-consistent pendulum equation are generalized to describe free-electron laser operation in higher harmonics; this can significantly extend their tunable range to shorter wavelengths. The dynamics of the laser field's amplitude and phase are explored for a wide range of parameters using families of normalized gain curves applicable to both the fundamental and harmonics. The electron phase-space displays the fundamental physics driving the wave, and we use this picture to distinguish between the effects of high gain and Coulomb forces.
248 citations