deletions | additions       diff --git a/section_Introduction_The_interaction_of__.tex b/section_Introduction_The_interaction_of__.tex  index 00a006a..6b7daf9 100644  --- a/section_Introduction_The_interaction_of__.tex  +++ b/section_Introduction_The_interaction_of__.tex 
...
This energy-loss phenomenon plays an important role in many experimental studies involving solids, surfaces and nanostructures [add citation].   The complexity of describing the dynamic interaction between charged particles and solids has initiated a large amount of research both experimentally and theoretically in recent years; in the latter the condensed matter community, however, have initiated sophisticated computer simulation techniques with considerable success.   Among the many measurable quantity the stopping power $\mathrm(S)$ \cite{Ferrell_1977} has received much attention; it provided detailed information regarding the energy transfer between the incoming projectile and the solid target.   The Varies models and theories have been proposed to calculate stopping cross sections $\mathrm(SCS)$; even today a unified  theoretical approach suitable for different projectiles and energies is not available in the literature. Bethe \cite{Bethe_1930}  models employed to study stopping of elementary charged particles in solids \cite{Bloch_1933,Bethe_1930} has stimulated this kind of study. In the low energy region the energy loss in metal is due to the excitation of a portion of electrons around the Fermi level to empty states in the conducting band. But at higher energies, a minimum momentum transfer of the projectile is possible due to its short duration close to the target. In this region the electronic curve has a maximum due to the limited response time of target electrons to the projectile ions.