The Energy-Loss Process

In thicker uniform samples the peaks at each mass broaden out with a relatively flat-topped distribution. By calculations based upon the energy loss process described above, it is possible to relate the energy of the scattered ion to the depth below the surface for the scattering interaction. In this way the observed distribution may be related to the composition vs. depth of the particular element within the sample layer. 

Nuclear collisions can become an important part of the energy loss process, especially in the case of heavy ions and fission fragments. The theory describing this process is too complicated for a brief summary. 

On the other hand, in the case = 7 we observe a different behavior. Here the non-linear values lie well below those of the linear calculation on the whole velocity range. The interpretation of these results is also very revealing. The results obtained from the dielectric calculation increase by a whole factor 49 when going from = 1 to Zj = 7 - as expected from a linear formalism. Instead, the non-linear results increase by a much smaller factor (a ratio about 20 between both maxima). This may be interpreted as a saturation in the energy loss process, i.e., the values increase by a much... 

Now we focus on the role that the excitation of e-h pairs and plasmons play in the energy loss process. First, we restrict our calculations to the Zj (linear) contribution to the stopping power of a FEG. Figure 2 exhibits the separate RPA e-h pair- and plasmon contributions to the Zj stopping power... 

Fig. 1. Schematic diagram of (a) transmission electron energy loss (b) reflection electron energy loss (c) excitation outside the surface in reflection electron energy loss (d) momentum conservation in the energy loss process.

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