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Mean free path
About: Mean free path is a research topic. Over the lifetime, 4412 publications have been published within this topic receiving 114418 citations.
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TL;DR: In this article, a theory of the thermal force acting on a spherical particle was obtained for the entire range of Knudsen numbers, in good general agreement with all experimental data and gives the correct dependence on the thermal conductivity of the particle.
Abstract: A linearized version of Grad's thirteen‐moment equations have been solved with generalized velocity slip and temperature jump boundary conditions, and a theory of the thermal force acting on a spherical particle obtained for the entire range of Knudsen numbers. The theory is in good general agreement with all experimental data and gives the correct dependence on the thermal conductivity of the particle. In the range of large Knudsen numbers the solution is functionally the same as Waldman's and also gives the correct infinite mean free path limit. As a by‐product of the theory, thermal accommodation coefficients can be predicted with fair to good accuracy. For particles of high thermal conductivity and high thermal accommodation coefficient, the theory also predicts the possibility of a reversal of the thermal force near the continuum limit.
58 citations
TL;DR: These are to the authors' knowledge the first measurements of the propagation of coherent, single-cycle pulses of terahertz radiation in a scattering medium as a function of the length L of the medium and extract the scattering mean free path l(s)(omega) over a broad bandwidth.
Abstract: We describe what are to our knowledge the first measurements of the propagation of coherent, single-cycle pulses of terahertz radiation in a scattering medium. By measuring the transmission as a function of the length L of the medium, we extract the scattering mean free path lsω over a broad bandwidth. We observe variations in ls ranging over nearly 2 orders of magnitude and covering the entire thin sample regime from L/ls≪1 to L/ls∼10. We also observe scattering-induced dispersive effects, which can be attributed to the additional path traveled by photons scattered at small angles.
58 citations
TL;DR: Theoretical derivations of the inelastic differential inverse mean free path (DIMFP) for electrons crossing solid surfaces were made for different crossing angles and electron distances relative to the crossing point at the surface.
58 citations
TL;DR: In this paper, a spherical electrostatic (Langmuir) probe in a slightly ionized plasma is studied from a kinetic theory point of view, where the velocity space is divided into two regions along the straight cone tangent to the spherical probe and different distribution functions are defined in the two regions.
Abstract: A spherical electrostatic (Langmuir) probe in a slightly ionized plasma is studied from a kinetic theory point of view. The two‐sided distribution function method of Lees, which embodies the Mott‐Smith approach, is used. The velocity space is divided into two regions along the straight cone tangent to the spherical probe, and different distribution functions are defined in the two regions. On satisfying the two relevant moments of the distribution function (continuity and number density flux) three simultaneous ordinary nonlinear differential equations, which are appropriate to all values of the Debye length, collision mean free path and probe potential, are obtained for determining the ion and electron number densities, and the potential. These equations reduce to the usual linear flux equations when the mean free path is much shorter than the probe radius and the Debye length. The equations are first linearized and solved for the case of small probe potential. Explicit solutions are given for the current‐voltage characteristics and the distributions of the number densities and the potential. The general case of arbitrary probe potential is also studied. Results for the characteristics and for the potential drop in the sheath are presented for some representative cases. Many of the results which are obtained do not appear in the original simplified Langmuir model. The modifications required to take into account the curvilinear orbits of the charged particles are discussed.
58 citations
TL;DR: In this article, a theoretical study of quantum charge transport in atomistic models of silicon nanowires with surface roughness disorder, using an efficient real-space, order N Kubo-Greenwood approach and a Landauer-Buttiker Green's function method, is presented.
Abstract: We report on a theoretical study of quantum charge transport in atomistic models of silicon nanowires with surface roughness disorder, using an efficient real-space, order N Kubo-Greenwood approach and a Landauer-Buttiker Green's function method. Different transport regimes (from quasiballistic to localization) are explored depending on the length of the nanowire and the characteristics of the surface roughness profile. Quantitative estimates of the elastic mean free paths, charge mobilities, and localization lengths are provided as a function of the correlation length of the surface roughness disorder. Moreover, the limitations of the Thouless relation between the mean free path and the localization length are outlined. © 2008 The American Physical Society.
58 citations