AbstractWe have calculated electron‐phonon matrix elements relevant for indirect optical absorption, intervalley matrix elements and intravalley deformation potentials as well as splitting parameters for thek=0states in silicon and germanium within the rigid quasi‐ion model. In contrast to the “atomic” potentials in conventional rigid‐ion models the quasi‐ion potentials are well‐defined. The agreement with experiment and with other theoretical results is satisfactory in most cases. We have also studied the role of distortion corrections to the rigid quasi‐ion approximation. We find that the influence of distortions is small, indicating that the rigid quasi‐ion model is an adequate description ‐ at least in case of