Selection Rules for Scattering Processes in Crystals

Abstract

Different approaches in finding selection rules for scattering processes in crystals are discussed. It is shown that both the subgroup and the full-group procedures lead, not only to the same selection rules, but also to the same formula for finding them. The final result is expressed in terms of characters of small representations of the groups of k, and it is a matter of taste which procedure to use in deriving the formula for selection rules.