Electron velocity, normal component

In the case r rtr we can write the following expression for the variation of the normal electron velocity component ... 

The reflection of the electron should be expected in the case r Tu-when the maximum potential energy of the electron in the evanescent wave is higher than its kinetic energy associated with its normal motion toward the dielectric surface (i.e., Umax > E ). The maximum normal velocity component of the reflected electrons is given by... 

Not discussed herein is very recent experimental work in which the thermal distribution of molecules and atoms of a cluster after surface impact has been measured and compared to information theory. There are two reasons why these results should be mentioned. One is that the experiment used a cluster beam incident at an angle (f) with respect to the normal. It measured the component of velocity parallel to the surface. But in the plane containing the incident beam, there are two such components. One at an angle tt — 0 with the cluster beam and one at an angle TT + (j>. The observed velocity distribution in both directions was identical. This is a computation-free proof of the equilibration. The other point is the magnitude of the measured temperature which was of the order of 15 000 °K, same as that measured for electrons boiling out of the impact. ... 

In the case of a two-dimensional metal, the Fermi surface can be represented as a circle, with velocity components along the x and y axes (Figure 13.4a). Because velocity states are filled up to the Fermi surface, when the metal is at normal equilibrium the velocities sum to zero. Thus, although the electrons are in motion, no current flows. 

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