Bremsstrahlung of Fast Charged Particles in a Solid Body

The cross-section of a photoprocess on an atomic ensemble (in case of a monatomic target) can be represented in the following form [1]: $$ d{\sigma_{{t\arg et}}}={{\left| {\sum\limits_j {\exp \left( {i\mathbf{q}{{\mathbf{r}}_j}} \right)} } \right|}^2}d{\sigma_{atom }}, $$