Mean free path reduction

The high density of states found in the 3c/bands of Fe, Co, and Ni leads to a reduction of the mean free path of the electrons in this band. This causes a decrease in their mobility and hence in the electrical conductivity of these elements compared to simple metals and copper where the conduction electrons are in s/p bands. 

Thus we find that, in this limit, the reduction of the exciton mean free path does not affect the radiative broadening RK, as noticed by Agranovitch,152 since ImX and RK enter the reflection amplitude (4.23) additively. This conclusion however does not hold for the emission, as we shall show in Section IV.A.4.b below. 

In general, low electron concentration and high mobility appear to depend most critically on reduction in nitrogen vacancies and a morphology in which polycrystallinity is not disadvantageous, provided crystallite interfaces are intimate and sizes are significantly larger than the mean free path determined by other scatterers. 

SOI and strained silicon transistors are comparable to or smaller than the phonon s mean free path (which, for silicon, has been estimated as 300 nm at 300K) [53], In this limit, the film surfaces alter the phonon dispersion relations [76], and the phonon-surface scattering may become the predominant scattering mechanism [3, 53], Since phonons are the main carriers of thermal energy in silicon, these effects alter the thermal conductivity, which differs from that of bulk silicon [10, 36, 77], Measurements of the thermal conductivities of silicon films of thicknesses down to 74 nm found a reduction of 50% with respect to the bulk value at 300K [53], This reduction depends on the temperature and the thickness of the film [3, 53],... 

With reduction of pressure the mean free path grows larger, and with it the resistance to mass transfer due to intermolecular collision is progressively diminished. At pressures corresponding to mean free paths larger than the dimensions of the vessel in question, the gas phase resistance to mass transfer is negligible and the only limiting factor on the rate of material movement is the rate of emission from the interface. 

Figure 30 compares the long-range diffusivity of n-butane in a loose bed of NaX zeolite crystallites with that of the same sample after compaction under a pressure of 2.5 MPa. It is found that long-range diffusion in the compacted material is reduced by a factor on the order of 3, which may be attributed to a reduction of both (diminution of the intercrystalline void volume) and (decrease of the intercrystalline pore diameters and hence of the effective mean free path). This experimental result confirms that the contribution of intra-... 

Size effects in the particle growth by deposition from the gas phase are related in particular to the Kelvin effect that decreases the saturation pressure near the particle surface with the reduction of the particle size and dependence of the sticking (condensation) coefficient on the particle size. Transfer of vapor molecules to the particle surface in the general case also depends on the particle size through the Knudsen number Kn that is equal to the ratio of the mean free path of gas molecules to the particle radius. Further we consider the free-molecular gas flow when Kn l. The particle growth rate is proportional to the trapping coefficient /i that is defined as the ratio of the resulting flux of vapor molecules into the particle to the flux of vapor molecules incident on the particle... 

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