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.

Thermal conductivity of tetrahydrofuran hydrate

Abstract: The thermal conductivity of tetrahydrofuran hydrate has been measured in the temperature region 2–220 K by the steady-state potentiometric method. The temperature dependence of the thermal conductivity exhibits behavior typical of amorphous substances. It is shown that above 100 K the mean free path of the phonons is considerably smaller than the lattice parameter and is no longer dependent on temperature.

Elastic scattering effects in the electron mean free path in a graphite overlayer studied by photoelectron spectroscopy and LEED

Abstract: The energy dependence of the mean free path lsEd in graphite at low kinetic energies sbelow ,50 eVd is studied using the synchrotron radiation excited Si 2p core level photoemission signal from a SiC substrate attenuated by an epitaxial graphite overlayer. Diffraction structure in lsEd, appearing as strong intensity minima in the Si 2p signal, is found to reflect band gaps in the unoccupied states of graphite. Furthermore, lsEd is derived based on analysis of very-low-energy electron diffraction data supported by calculations of the complex band structure of unoccupied states, where lsEd appears from the Bloch wave damping factor. Conceptually different, the two methods yield equivalent lsEd. The strength of the diffraction structure in lsEd manifests a significant elastic contribution to electron scattering at low energies, sharply increasing in the band gaps of the unoccupied states.

Interplanetary transport of solar electrons and protons: Effect of dissipative processes in the magnetic field power spectrum

Abstract: Quasi-linear theory describing charged particle transport in interplanetary space within the framework of a slab turbulence picture was for a long time confronted with the problem that the theoretically predicted mean free path for scattering at magnetic field fluctuations was too small when compared with the corresponding parameter derived from fits to observed intensity and anisotropy profiles of solar energetic particles. The theory up to now has neglected the dispersiveness of some of the scattering plasma waves and the effects resulting from the finite temperature of the plasma through which the particles propagate. We have therefore attempted to give a more realistic model of an observed interplanetary turbulence spectrum. The most simple picture we find requires the dissipation range to be constituted by parallel dispersive whistler, electron and ion cyclotron waves in a warm plasma (β ≈ 1). The dispersion relation of heavily thermally affected ion cyclotron waves needed in this model is calculated for the first time. The model is fitted to the turbulence spectrum measured on June 7, 1980, by ISEE 3 (ICE). The derived model parameters are used in a quasi-linear calculation of both proton and electron mean free paths. As a first step resonance broadening due to wave damping is neglected. The results are compared with typical empirical proton mean free paths and with electron mean free paths obtained from fits to electron intensity and anisotropy profiles observed simultaneously by the same satellite. In both cases the theoretical values seem to be systematically larger than the empirical ones. Thus scattering enhancements by nonlinear or thermal resonance broadening or oblique waves now bear the hope to remove the discrepancy between theory and observation.